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Discussion Starter · #1 ·
For years the red glow of the SRS warning lamp has been my constant driving companion. Shorting the Service Check Connector on the passenger's side yielded a DTC (error code) of 5-1 - "Internal fault in the SRS unit." Clearing this error code with the Memory Erase Signal Connector (MES) under the dash only worked until the next time I started the car, when the SRS indicator would illuminate again. Unwilling to pay for a new SRS unit, I just lived with it, uncertain whether or not the airbags would deploy in an accident.

Last week my car failed to start due to a dead battery. I replaced the battery - it was 8 years old - and when I started the car the SRS light went out. That was the first time in four years that the SRS light stayed off while the car was running.

Why would a new battery cause the SRS light to go out? Curious, I discovered in the Service Manual (Helm) and in Honda Service News (November 1997) that low battery voltage or problems with the charging system can cause the 5-1 or 9-2 internal SRS module errors. Apparently, the SRS module self-check procedure has stringent voltage thresholds, and values above or below these strict limits can trigger an error code. Even a battery good enough to start the Odyssey through years of harsh Michigan winters had not been good enough to meet the SRS voltage requirements.

[From the service manual: "When you keep the ignition switch turned ON (II) or keep the engine cranking with low battery voltage (discharged battery), this may be self-diagnosed as a failure in the SRS system, and the SRS indicator light may indicate...DTCs 9-2, 5-1." From Honda Service News 11/97: "A battery that's not fully charged can set an SRS DTC. In the S/M, these DTCs are listed as an 'Internal failure of the SRS unit,' but low battery voltage can also cause them."]

Of course, "Internal failure of the SRS unit" is a misleading term for an error really caused by low battery voltage rather than a faulty SRS module. Honda Service News recommends testing the battery and charging system as the first step in diagnosing these errors. (I wonder how many SRS modules have been replaced when the real culprit was a bad battery?)

The happy ending to my 4 year SRS saga was spoiled a couple days after I replaced the battery when I realized that the SRS light wasn't illuminating at all - even during the initial ignition-on test period. Apparently the SRS indicator bulb had burned out right after I replaced the dead battery. So had I really done anything to cure the SRS problem, or was I just deceived by the weird coincidence of failed indicator bulb at the time of battery replacement? To find out, I replaced the SRS indicator bulb and cleared the SRS memory. Much to my relief, the SRS indicator lamp now functioned normally - it illuminated during the initial self-test period and then stayed out after the car was started. So the new battery really had cured the SRS problem after all and the burned out bulb was just a coincidence.

I should mention that my previous attempts - years ago - to clear the SRS indicator light by way of the Memory Erase Signal Connector were misguided and were based upon a misunderstanding of how the SRS indicator lamp functions. I've since realized that in addition to the initial ignition-on period, there are two different kinds of states that can cause the SRS light to be illuminated. One is when the continuous SRS module self-testing process finds an on-going error. The second state is when there is no on-going error found, but a previous stored error code remains in SRS memory. Either one of these two conditions causes the illumination of the indicator light. If the SRS module has found an on-going error, there is no point in clearing the SRS memory register, since the SRS module will immediately re-store the current DTC code in the recently cleared memory. It would be like trying to remove water from a tub while the faucet is still turned on. Whatever you remove is immediately replaced.

The only time it makes sense to clear the SRS memory via the MES connector is when there is no on-going DTC. In this situation the SRS light is illuminated because a copy of an old - now corrected - DTC is still stored in memory. Only under these circumstances will use of the MES turn off the SRS light. What this means is that the MES connector cannot be used to "reset" or "clear" a current error in the SRS module. If an error state exists, nothing you do with the MES will fix it. If the error condition has been corrected, and the old error code persists in memory, then you can use the MES to clear the code from memory and thereby turn off the SRS indicator.

How can you tell if the SRS light is illuminated because of an on-going error or because an old error is still stored in memory? When you short the Service Check Connector, an on-going error will flash in an infinitely repeating loop. (E.g., 9-2, 9-2, 9-2, 9-2, etc, etc, etc.) If there is no on-going error, but an old error code remains in memory, then the DTC will be flashed only once. So, if you run the diagnostic procedure and find a DTC flashing repeatedly, don't bother clearing the SRS memory. You need to fix the cause of the problem before you do anything about clearing the SRS memory. If the DTC flashes only once then you can erase the SRS memory as a means of turning off the indicator light.


Since replacing the SRS indicator bulb wasn't an entirely straightforward process and isn't covered in the Helm manual, I thought I would recount the procedure here:

1) Remove the small vent just to the left of the instrument cluster. Just pull it straight out.

2) Behind the vent you will find one of the three screws holding the instrument cluster cover in place. The other two are found at the inside top of the cluster cover. Remove the cover's three screws.

3) With the instrument cluster cover removed you will see four screws holding the instrument cluster to the firewall/dashboard. Remove these four screws.

4) Carefully pull the gage cluster forward. Now try to locate the SRS bulb. Surprise! There is a tiny circuit board in the place where the bulb should be. Unlike the other dash bulbs, the SRS bulb is mounted on a tiny circuit board. To get to the bulb, first remove the yellow wire connector attached to the back of the small circuit board. The circuit board is held in place by a white plastic tab which pulls out from the main instrument board. Before removing the white plastic tab I removed the three light bulb holders in the area closest to the SRS indicator circuit board. This takes some pressure off the main instrument board's flexible circuit "sheet" and reduces the likelihood that you will tear the circuit sheet as you remove the SRS indicator circuit board. (Since the large flexible circuit sheet partially covers the SRS indicator board, if you aren't careful pulling out the SRS circuit board you may damage the large flexible circuit sheet.)

5) The SRS bulb is similar to the type described in this thread about the Odyssey clock light http://www.odyclub.com/forums/showthread.php?s=&threadid=23429&highlight=climate+lights. I used the same Radio Shack "micro lamp" recommended in that thread. To replace the bulb you need to pull the small square black rubber bulb holder off the two metal prongs on the SRS indicator circuit board. With the rubber bulb holder removed you can extract the old bulb and its wire leads and then insert the new bulb in the bulb holder, being careful to route the wire leads so they will be in contact with the two prongs on the circuit board when you push the rubber bulb holder back in place. I purchased my new bulb at Radio Shack - #272-1092 - for $1.79. My local Honda parts counter didn't have replacement bulbs, but they did offer to sell me a new SRS indicator circuit board with bulb installed for $34.

6) Push the bulb holder with the new bulb down onto the two circuit prongs. Temporarily connect the SRS lighting harness to the SRS indicator circuit board and test the new bulb. It should light for around 6 seconds when the ignition is turned on. (Of course it won't go out after six seconds if the SRS unit discovers an error or if a previous error is stored in the SRS module's memory.)

7) Remove the yellow harness from the indicator circuit board and reinstall the indicator circuit board in the back of the instrument cluster. Install the white tab that locks the SRS indicator board into the back of the instrument cluster. Be careful not to tear the circuit sheet that runs the length of the back of the instrument cluster. Replace any other bulbs in the instrument cluster that you previously removed to facilitate handling the SRS indicator circuit board.

8) Reinstall the four screws holding the instrument cluster to the bulkhead and the three screws holding the cluster cover in place. Install the vent to the left of the cluster - just press it back in place.

That's it!

daneli
1996 Honda Odyssey
2000 Honda Odyssey
 

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Great thread! Any chance you could give a quick tutorial on checking the SRS light codes? My SRS light is on and after a reset will sometimes stay off for a day and sometimes stay off for a couple of months. Would be nice to know what the problem is. Thanks.

On a side note, the same thing happened to my old civic. The SRS light came on because of a slowly dying battery. After installing a new battery the light was still on. The stealership I took it to wanted $600 to replace the alternator and couldn't guarantee it would fix the problem. They also wouldn't clear the SRS light, I suspect cause they knew it would not come back on and I would have a reason to spend $600. Well, I did not replace the alternator and found reset instructions a few months later. The light went off and stayed off until I sold it 4 years later.
 

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Discussion Starter · #3 ·
"Any chance you could give a quick tutorial on checking the SRS light codes?"

Sure. Here's a summary of SRS diagnosis. To read the Diagnostic Trouble Codes (DTCs) you need to short the Service Check Connector (SCC) on the passenger's under-dash area (near the center console). A plastic cover may need to be removed to get access to the two prongs of the SCC. With the ignition off, create a connection between these two prongs. For example, you can use alligator clips or open up a paper clip and push an end into each side of the Service Check Connector. Now, when you turn on the ignition the dashboard SRS light will act as an output device for the SRS computer module.

Here's the type of output you can get from the SRS system:

1) If the SRS light blinks evenly on and off, then the system is normal.
2) If the SRS light blinks in a repeating series of long and short pulses, there is an on-going error. The long and short pulses (E.g., 9-2) represent the Diagnostic Trouble Code.
3) If the SRS light displays a single set of long and short pulses and does not repeat in a loop, then there is no current DTC, but an earlier DTC is stored in memory. (This could be an intermittent error or a problem you previously fixed.)

The system can display multiple error codes, with each DTC repeating in turn. It can also display a mix of intermittent and current errors, by flashing the intermittent error code(s) only once, and then following with the repeating display of any on-going error(s).

If the SRS light stays off completely, and won't illuminate during the ignition-on self test, then the SRS indicator bulb is out, the dashboard SRS indicator circuit board has failed, or there is a problem in the harness wiring between the SRS indicator circuit board and the SRS computer module.

The Service Manual lists 12 SRS Diagnostic Trouble Codes:

1-1, 1-2, 1-3 & 1-4: Driver side airbag wiring problems.
2-1, 2-2, 2-3 & 2-4: Passenger side airbag wiring problems.
5-1 & 9-2: SRS module internal errors.
9-1: Indicator light circuit board and/or wiring problem.
10-1: SRS module inoperable and must be replaced - no troubleshooting procedure for this code.

Notes:
1-x (driver side) problems are probably more common than 2-x (passenger side) problems due to the relative vulnerability of the driver's cable reel.
5-1 & 9-2 are often caused by battery or charging system issues.
9-1 is by definition likely to be an intermittent error, since you wouldn't be able to read this DTC at the same time the SRS light isn't working.
10-1 - ? I'm not sure about this one - it may come on after the airbags have deployed.

If you get 5-1 or 9-2 it makes sense to look for a bad battery, poor battery cable connections, poor ground connections between the battery and the chassis/engine block, and over- or under-voltage from the alternator. If you get no SRS light at all you can check the dashboard SRS indicator circuit board for a blown bulb.

Beyond these steps, troubleshooting airbag wiring problems without a Service Manual is dicey. To be safe, you need to read, understand and follow the directions and precautions for the SRS enumerated in the Manual. The Service Manual insists on several layers of precautions and these extend beyond obvious stuff like disconnecting the battery. (The SRS capacitors remain charged for a few minutes after disconnecting the battery.) According to the Service Manual, you should never disconnect the main SRS harness without first disconnecting and electrically disabling the airbags, using the procedures described in the Manual. Caution is also called for when using an ohmmeter to test the SRS harness, since doing this incorrectly can deploy the air bags.

Airbags save lives, but placing explosive charges in a passenger vehicle aimed at the head, neck and chest of occupants comes with some risks. Apparently messing around with the SRS wiring is a good way to have a close encounter with one of these risks. Nevertheless, I don't think we should get undone by the risks of the SRS system. Working on cars means being in close proximity to explosive fuel, dangerous battery acid and the like. People have done this safely for years by being methodical and cautious and by thoroughly understanding and managing the risks involved. The same approach will work with SRS troubleshooting as well.
 

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Discussion Starter · #6 ·
Update:
When the weather turned cold last winter I was disappointed to find that the SRS light came back on. The DTC was always the same: 5-1. Furthermore, the fault was always intermittent. That is, when I shorted the Service Check Connector (SCC), the 5-1 code flashed only once, indicating that the fault - previously stored in memory - was now resolved.

Every time I cleared the 5-1 code the car would run for a few days with the SRS light off, but eventually it would illuminate again. If the light is going to come back on, it only does so when the engine is being cranked by the starter motor. Otherwise put: If the light goes off at the end of the initial power-on self-check, then I know that it will stay off at least until the next time the car is started.

This last fact is an important clue as to what is going with these defective SRS modules. When you turn the ignition in the Odyssey to the II position, the SRS unit begins its initial power on self-test. This initial test runs for 6 seconds. During the initial test the SRS light is illuminated. (And you hear 6 warning beeps if your seatbelt is unlatched.) If the self-test is passed, the SRS light turns off.

Because most people start the car (move the ignition to the III position) immediately after placing the key in the ignition, it is almost always the case that the SRS initial power-on self-test and the cranking of the engine by the starter motor happen simultaneously. But you can separate these two events by not turning the key to the III position until after the SRS unit completes its 6 second power-on self-test.

I tried this as an experiment. That is, I tried for several weeks to remember not to start the car until after the completion of the 6 second SRS self-test. Surprise! The SRS light always went out at the end of the initial self-test period.

If your SRS light is on and you have DTC code 5-1 you can try this yourself:

1. Clear the SRS light via the MES connector.
2. When you start the car, turn the ignition to the II position and wait for the 6 second SRS self-test to complete before turning the key to III to engage the starter motor.

If your SRS unit is like mine, as long as you remember not to start the engine until the 6 second test is complete, then the SRS light will turn itself off and stay off. If you forget to wait until the 6 seconds are up and if the SRS light comes back on, then you will have to use the MES procedure to clear the light before you start the experiment over again.

Why does this work? Apparently voltage drops enough during engine cranking to trigger a warning from the SRS unit. Once the car has started however, the voltage is restored to an adequate level. That is why the 5-1 code always appears as an intermittent error. The error condition exists only during engine cranking.
 

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Sticky!
 

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i reasently purchased my ody and found the srs light to be a huge concern as such ive been putting aside to find the remedy but now that you mention your soulotion i feel it is the same cause for my srs light . .... my windows roll up slowly my dash lights dim when i turn up my radio and when i turn on the ac ... i don't know why i didn't think of this eairly on thanks for sharing the info i'm getting a new battery tomorrow
 

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I agree with all the diagnosis but one. I don't think it is the drop in voltage is the problem but the filtering ability of the battery. The battery acts as a large filter to filter the elictrical noise in the system. Honda puts a subpar battery in the Odyssey with low CCA for the electrical system of the van. When replacing it you should not use just a direct replacement but as large a battery that will fit.The starter motor will put a lot of noise in the system so you need a lot of battery filtering capacity. Back in the early days of computers they had massive power supplies. We used wet cell batteries as filters as they had a lot more filtering capacity in a smaller space than capacitors.
 

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Thanks for the thread.

I just cleared my SRS, hopefully it stays off. Stayed off after 30 seconds so assuming it'll be alright.

Had a HID bulb go berserk on me and threw the SRS light on a year ago.

When HID bulbs decide to go, they put on quite a show.
 

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I am looking for my SCS service connector on my 2002 EX.

Page 23-32 of my Helm shows what looks like a female connector hanging down in front of the drivers side under-dash fuse box. I cannot find any connector in this location.

All I can find is a male connector, pastel green in color, taped to the wires going to the brake switch, with a blue and black-with-silver-stripes wire coming out of the connector.

The SCS shorting tool is a female connector.

Can anyone help with locating my SCS service connector? My SCS light is continuously on.

Scan Gauge says "no codes found -- ready."

Since I posted the above, I found post

http://www.odyclub.com/forums/showthread.php?threadid=35589

that indicates that my SCS service connector is called the Memory Erase Signal, MES, connector and it is a yellow plug that is plugged into the fuse panel.

So I will go with it.
 

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Stuck a couple of paper clips in the MES connector and shorted them with a couple of standard Radio Shack alligator clip test leads, turned on the ignition and did the open, close, open within the 4 second time limit and got the two blinks indicating reset.

After turning ignition off for 10 seconds and then on again, the SRS light goes off.

We will see if it holds.

I had to repeat the procedure several times until it worked and finally figured out that I was rushing and not waiting for the light to come back on and then go off before making or breaking the connection.

Thanks all!
 

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William Wiles said:
I agree with all the diagnosis but one. I don't think it is the drop in voltage is the problem but the filtering ability of the battery. The battery acts as a large filter to filter the elictrical noise in the system. Honda puts a subpar battery in the Odyssey with low CCA for the electrical system of the van. When replacing it you should not use just a direct replacement but as large a battery that will fit.The starter motor will put a lot of noise in the system so you need a lot of battery filtering capacity.
There are two power inputs to the SRS computer.

Has anyone experimented with adding power diodes and large capacitors to these two lines to get the computer power filtered and stable during the cranking period?

I'm considering adding these items to the power supply wires, and I'm hoping there's room in the area of the computer to mount them.

Anyone have any idea of what the static current draw for this computer is so I can calculate the capacitance required?

Pop
 

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William Wiles said:
I agree with all the diagnosis but one. I don't think it is the drop in voltage is the problem but the filtering ability of the battery. The battery acts as a large filter to filter the electrical noise in the system. Honda puts a sub par battery in the Odyssey with low CCA for the electrical system of the van. When replacing it you should not use just a direct replacement but as large a battery that will fit.The starter motor will put a lot of noise in the system so you need a lot of battery filtering capacity. Back in the early days of computers they had massive power supplies. We used wet cell batteries as filters as they had a lot more filtering capacity in a smaller space than capacitors.
I replaced my OEM battery 6 years ago with an Odyssey (no relation to Honda Odyssey) model PC1200MJT. I regularly hook it up to a Deltran Battery Tender. Service life is 6 to 10 years so I am about ready to replace it.

http://www.odysseysoutheast.com/pc1200-battery.php

 

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daneli1 said:
"Any chance you could give a quick tutorial on checking the SRS light codes?"

Sure. Here's a summary of SRS diagnosis. To read the Diagnostic Trouble Codes (DTCs) you need to short the Service Check Connector (SCC) on the passenger's under-dash area (near the center console). A plastic cover may need to be removed to get access to the two prongs of the SCC. With the ignition off, create a connection between these two prongs. For example, you can use alligator clips or open up a paper clip and push an end into each side of the Service Check Connector. Now, when you turn on the ignition the dashboard SRS light will act as an output device for the SRS computer module.
This must be for your 1996?

My manual for the 2002 requires connecting a "Honda Program Tester" to the 16 pin data link connector under the driver's side dash in order to "short the SRS terminal." When the ignition is turned on the SRS indicator will indicate the Diagnostic Trouble Code by the number of blinks.

If I can figure out the pin assignments I could use a paper clip or make a 16 pin connector with the appropriate terminals shorted.

I think I have to short pin 4 (chassis ground, upper middle) and pin 9 (SCS, service, lower left).

Anyone?

P.S. And here is the OPDS unit warranty extention for 2002 ODY's:

http://www.skidmore.edu/~pdwyer/e/files/campaign_and_recall_bulletins/A06-009.pdf
 

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Discussion Starter · #16 ·
Has anyone experimented with adding power diodes and large capacitors to these two lines to get the computer power filtered and stable during the cranking period?
This sounds like a good idea. The module itself uses 4 large capacitors to store the required 12 volts. Maybe these capacitors degrade over time?

 

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Where is the airbag control module located in a 2005 Ody?
 

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"Any chance you could give a quick tutorial on checking the SRS light codes?"

Sure. Here's a summary of SRS diagnosis. To read the Diagnostic Trouble Codes (DTCs) you need to short the Service Check Connector (SCC) on the passenger's under-dash area (near the center console). A plastic cover may need to be removed to get access to the two prongs of the SCC. With the ignition off, create a connection between these two prongs. For example, you can use alligator clips or open up a paper clip and push an end into each side of the Service Check Connector. Now, when you turn on the ignition the dashboard SRS light will act as an output device for the SRS computer module.

Here's the type of output you can get from the SRS system:
Can anyone tell me which pins i need to jump on a 97 Oasis? Resetting the srs light just doesn't do it. Need to read what codes it has. Not sure if it's pin 1 and 4 or 1 and 6 ?
 
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