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How to Perform the "Jump the SCS Line With the HDS" Procedure Without the HDS

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104K views 138 replies 7 participants last post by  John Clark  
#1 · (Edited)
How to Perform the "Jump the SCS Line With the HDS" Procedure Without the HDS

I recently did some troubleshooting of my radiator/condenser fan circuits using the Factory Service Manual. If you have the Factory Service Manual then you may have noticed that when you are troubleshooting an electrical problem that involves a connection to the PCM, the procedure will often have you check wiring between the component you're testing and the PCM. To do this you need to unplug the connectors to the PCM. When that is required the procedure always says to "Jump the SCS line with the HDS." It says that this step is required to prevent damage to the PCM when disconnecting. Even when the key is turned to LOCK (0) the PCM continues to monitor the EVAP system for up to 30 minutes. Honda says that if you disconnect a harness from the PCM during this window you risk damaging the PCM. To prevent this they tell you to jump the SCS line with the HDS. This is done after you turn the key to the LOCK (0) position. They instruct you to use the HDS to jump the SCS line and then remove your PCM connectors and do your testing. Once you're done, you reconnect the PCM and then un-jump the SCS.

Well, obviously most of us don't have the HDS bidirectional scan tool for doing this. After some Internet research it's clear to me that all this procedure does is short pin #9 (SCS line) to pin #4 (chassis ground) on the data link connector (DLC.) There are multiple ways you could do this. You can use a wire and hope you don't damage the the computer by connecting to the wrong pins, and/or if connecting to the front of the connector, hope you don't damage the connector. When diagnosing electrical problems, front probing a connector is always a big no-no due to possible damage to the connectors preventing the connector from making contact when you're done. If you put your wire on the back of the terminal (called backprobing) you still risk shorting the wrong pins, or the wire could fall out while you're conducting your test.

So, in order to make an easy way to do this while troubleshooting I decided to make myself a custom SCS Line Jump connector. For less than $6 shipped I bought a cheap DLC connector on eBay:






Link to pinouts for Honda DLC:

Honda OBD II diagnostic interface pinout diagram @ pinoutsguide.com


As you can see below, I simply soldered a jumper wire from pin 4 to pin 9 on the inside of the plug. So, for less than $6, and less than 10 minutes of time, I have an SCS line jumper connector to put the computer into test (apparently that's what jumping the SCS does) so that removing a PCM connector doesn't damage the PCM. If any of you watch the South Main Auto channel on YouTube, I asked Eric O (one of the top electrical diagnostic guys, and overall mechanic, on YouTube) if he ever did this in his diagnosing and he said no, and that if he needs to pull a connector he just pulls it and has never had an issue. Though, full disclosure, he always says the big three, Chrysler, GM, and Ford, are what keep him in the auto repair business--the Hondas, Toyotas, and Nissans just don't break as often. Anyway, there's probably only one very obscure instance where a PCM was damaged by pulling a connector and that led to putting the procedure in the book. However, for not even $6 it's cheap insurance if you find yourself needing to unplug the PCM during diagnostics. I simply tossed it in the bag with my scan tool and it will be ready the next time I hit that "Jump the SCS Line with the HDS" hurdle in the book.



Some pics:











 
#2 · (Edited)
good stuff John!
I do watch Eric O. Hands down best stuff on youtube for auto repair.
I like Ivan, EricTheCarGuy and BrianMobile1 as well, but Eric O is killing it.

I have done SCS line with a simple jumper before, iirc.
It is needed to reinitialize ABS/Traction control sensor in Honda/Acura
My autel 802 also has something in it for this as well, but I have not figured it out yet.
 
#4 ·
Eric O is just beyond super. I've watched all his videos and some of them twice.

I'm wanting to get a better scan tool but deciding on one is difficult. I currently have an Innova 3130 which does live data but no graphing unless I save the max of 20 frames it can save and go graph it on a computer. Full Bidirectional costs way too much for a DIY'er but before getting to that level what is the best one to buy to at least be able to do as much of what Ivan, Eric, ScannerDanner and those guys do as possible? Which Autel 802 do you have? I looked at the md802 Elite which has some graphing functions on it. Is that what you have? Do you like it?

I'd use it on the four vehicles in my sig.
 
#5 ·
Been there, done that. Last summer I was nearly set to by Autel 905 or DS708, instead I ended up with Autel MD802 (4 systems), which does all functions.
Autel

For my Honda it is able to scan all specialized modules and read/erase B codes, which regular OBD2 scanners can't read.
I have used it with my Maxima to see TPMS pressure, when I had to replace TPMS sensor. Note, it does not do TPMS activations.
It also not bi-directional.

I have had it over a year and very happy with it. The price is definitely a big plus. It comes with a year worth of updates. After that, you have to buy subscription in order
to keep updates flowing. It is an advanced scanner, which will read most native modules on almost any car. It has paid for itself, since I work on cars as a side hobby, so it sees many cars.
I have even used it on OBD2 cars that have native communication via special connectors. Two cars that come to mind are 2001 MB E320 that uses a gigantic round connector and 1998 Jeep wrangler that requires special Dongle. For both of these I used adapters from DS708 system. Worked a charm and read full diagnostics.

Watching Eric O operate the Verus with oscilloscope, makes me want to get one bad. But cost is beyond crazy. You can go separate scope path, with something like Pico.
Bi-directional is certainly awesome for troubleshooting. Most of the jobs I get are mechanical in nature, so I make do with what I have for now.

It would be great to acquire older Verus, but as you saw in Eric O video's he had a tough time with it breaking on him all the time, until he upgraded to the new Verus D10.
Ivan is still rocking his older Verus w/o apparent issues though.
 
#6 ·
I get confused on the subscriptions/updates. Are the updates just for newer year model cars? What happens with the 802 after the year of updates is out? I can't find what it costs to keep it up.

I found info on some of the Autel bidirectional models that talked about it being $20/mo for each make of car. That's not a great option for a DIY'er. Spending $1k or more isn't really an option either, though I considered it but the subscription fee on top of that wasn't an option. The 802 is around $200 on eBay so not bad at all. There just doesn't seem to be anything in between that and the $1K and up models.

I watched his magic with the scope and loved it but, yeah, I did notice he spent a lot on repairs.

Another hobby of mine is repairing old Tektronix analog CRT oscilloscopes (circa 1950-1985.) I have a Tek 475 (200Mhz scope, portable but big, but no storage capability.) But I also have a Tek 314 AC and 12-24VDC powered 10Mhz Storage Scope. Thanks to Eric I've figured out how to hook that thing up to an O2 sensor and read and interpret what it's doing. I don't have a digital storage scope, though.

The scan tool dilemma has been bugging me for a while.
 
#7 ·
Updates could introduce new model/year of coverage, bug fixes to the software or new functions all together.
First, warning on buying Autel. There seems to be a lot of "grey" market units. They will not let you activate them or download updates or use usa warranty service.
I did buy on eBay, but made sure it was legit USA model. The seller delivered as promised and I had no issues updating or registering the unit.
For one year, (starts when you first register unit on Autel.com) you will get free updates. After your year is over, the software level stays the same and no longer updates.
You can continue using the system w/o issues though. I view it akin navigation update from Honda, I can buy it once in 5 years and all the missing updates will be included.
Unless you are constantly scanning newly released cars, this should not be a big issue.

I just checked, you can buy updates for another year for $100 for MD802. If you go onto tooltopia.com and type in autel, they sell update cards for different autel units for 1 and 2 years worth of updates. It is inevitable that the cost of updates will be a significant cost of original unit.

here is another site that sells updates
Update Service

So buy something like Maxisys 908p and then you have to shell out over a grand each year to keep it up to date. I am sure Verus is much more expensive to keep up to date.
Consider the costs of running a shop. He also pays alldata and other online services that he mentions, for service manual access.
The costs add up quick....

I also work on a lot of side projects. Small engine work, fixing cell phones and tablets (mainly screens), fixing computer/tv components that die from bad Caps.
But I enjoy cars the most. Just finished Head job on VW Golf 2.0, mouse made a nest in the crank gear area and belt jumped. Bent all 8 valves and all the fun that goes with it.
 
#17 ·
...First, warning on buying Autel. There seems to be a lot of "grey" market units. They will not let you activate them or download updates or use usa warranty service.
I did buy on eBay, but made sure it was legit USA model. The seller delivered as promised and I had no issues updating or registering the unit.
Do you have a link to the seller you bought from? I'm probably going to get one of these. It's the one I was looking at to begin with. The ds708 is almost affordable but, you're right, the md802 is affordable enough you could still get something more later if you wanted to.
 
#8 · (Edited)
Thanks. Yeah, I did read about the knock offs. Thanks for the clarification on updates. That's what I figured but wasn't quite sure.

I did read about the SnapOn tools that if you don't update then you have to pay for all the missed updates to get the latest. You don't get out of paying. SnapOn knows how to soak the money out of you. Wasn't sure if some of the others did that too.

The cost of that stuff is why shop rates get so high. You have to have access to all that data and then be able to diagnose and fix with it. Most shops get the first part but many have difficulty with the second.

I, too, fix everything from cars to cell phones to household repairs. I repaired my Tektronix 475 CRT oscilloscope before I really knew what to do with one. They have some super documentation with those old scopes...like nothing you've ever seen before. I fixed my house R22 AC systems that had slow leaks with some R22 gauges and a couple of cans of "AC Easy Seal." One does what one has to do. That AC Easy Seal stuff could be the topic of another thread on another forum. I'm not usually a fan of that stop leak stuff for AC systems but for very slow leaks in an evaporator coil AC Easy Seal is great stuff! Hoping to buy another few years before having to replace the units.
 
#9 ·
They are not knockoffs, they are same units but designed for different part of the world. Basically ensure that they sell you a USA unit.

Sounds like you are a handy guy that everyone calls, not unlike myself :)
 
#10 ·
They are not knockoffs, they are same units but designed for different part of the world. Basically ensure that they sell you a USA unit.
Ah, got it!

Sounds like you are a handy guy that everyone calls, not unlike myself :)
Jack of all trades...master of none! (well, except flying corporate jets for a living...pretty much a pro there.)
 
#13 ·
I am presuming this precaution is also needed on the 2nd gen Odyssey aka 99-04 model years as the OBD-II protocol was not changed between the generation.

Completely off-topic but why not? I have got a vintage Onkyo TA2047 cassette deck. I had not powered it on in decade(s). Out of blue it has developed a peculiar problem. When I press the play soft-touch button, head moves but immediately half-retracts and the tape just keeps on spinning. I have verified that all three motors are working. The capstan is spinning. The pinch roller is free to rotate.

I found the service manual but I could not locate the mechanism or the logic which moves the head in to position or half retracts.

I am wondering if few of you guys could look at the schematics and offer some suggestions? Take it as a challenge!
 
#14 ·
It almost sounds like a mechanical issue to me...something isn't locking it into place? Dirty or sticky grease maybe? I've had poor results repairing that type of stuff but sometimes get lucky. If it's electronic you can get a part, probably. If it's mechanical it's done.
 
#16 ·
I have also seen alot of "rubber bands" which drive motor in this type of electronics. The rubber dry rots and either falls off or slips. Verify by opening the unit.
 
#19 · (Edited)
Thanks! Looks like he's up to $249 now.

I notice there's the md802 4 system and the md802 plus that does "all systems." The 4 system is $249 and the Plus is $299. Is it worth the extra $50 for the all system model?

Edit...nevermind. I see you said "All sys." I wonder why they went up so much in price in a year?
 
#20 · (Edited)
The only legit USA unit is All systems. When I was buying, I actually called Autel to clarify. They do have very confusing labeling system. Anyway, I edited my previous message before replying, get All systems unit.

There are plenty of other sellers with price closer to what I paid. I suggest you check sellers feedback to make sure that items are legitimate. It will be obvious right away. Plus you always have ebay buyer protection. Dont pay 300.
 
#21 ·
#26 ·
#27 ·
John,
as far as I know, there are two models of this scanner.
There is 4 systems and All systems. The DS stands for data streaming or some such thing.
Anyway, contact the seller and as long as the unit is All systems and will register and update in USA, you are golden.
I can't explain price difference other than its eBay.
I just bought 6 Denso brand new plugs on ebay in Nissan packaging for $42.5.
Whereas some sell single plug for $15+.
You can also call Autel directly, get their number from the website. I remember when I called
confused about all the different scanners and they politely answered all my questions.
IIRC, 4 system unit was made for other countries markets and not officially sold in USA.

here is one of the reseller sites:
$229.99 AUTEL MaxiDiag Elite MD802 4 system / All System + DS model + EPB + OIL Service Reset and support data stream function Engine + Transmission + ABS + Airbag + Major Electronic Models

you can see that they sell 4 system unit and for an extra $40, they will sell you All system unit.
let me know how you make out
Max
 
#29 ·
And to make matters more confusing here's a seller that appears to offer the same scanner for two very different prices. I've got a message into this seller RE the $235 one to make sure it's USA updatable and warranty is good. If you start looking close at all the listings I think most of them listed are probably coming from the same place. They all are from Los Angeles and the listings will say things like:

"Who We Are?

Specialized dealer of On-Board Diagnostic tools and automotive electronics for

more than 5 years.

Authorized first class distributor of Launch and Autel brands.

We are honesty and trusty, if you have some problems, please firstly contact us, then we will solve it for you once we are on working.Please be easy!"


Well, at least they're "honesty and trusty!" Maybe I just need to be more easy!

$235
Autel MD802 All System DS Model Scanner Diagnostic ABS Airbag EPB TPMS Oil Reset | eBay

$300
Autel MD802 All System OBDII Diagnostic Code Reader ABS Airbag Engine EPB TPMS | eBay
 
#30 ·
The $300 one says "US Stock,ship by UPS,100% Original, warranty and Update" right under description
another says nothing in that regard. Email the seller and ask. Description seems 100% identical.
Could be US model vs Non-US ???

Try bidding on this one and see how high the bidding goes, I think I did not do "buy it now" and bid in increments instead.
DS Model Autel MD802 All System OBD2 Diagnostic Tool Code Reader EPB DPF ABS | eBay

Yes, all of these sellers are primarily from China with some drop shipping from US. It is tough to communicate at times,
but they seem to play by ebay rules and will try help you in case of problems.
Case in point, when I bought my Autel, the OBD2 connecting cable connected fine to my Ody, but did not go well on my Maxima.
I contacted them and they sent me replacement cable.

If you get assurance from seller that what you are buying is a US ALL systems model, then if you get anything else you will have
ebay protection, and will not be responsible for return shipping or any charges at all.
 
#31 · (Edited)
I have one these Autel older regular models I got a few years back. Been working fine. I think I paid around 30 or 40 at the time as buy it now. I really needed one and it worked out for all our Toyota and Honda cars.

Edit: There is another 802 in the starting at 74. Maybe that might be the start they are expecting because other bids are already about there.
 
#32 ·
Yeah, I saw that one up for bid and was already considering it but haven't bid yet. Bidding always looks great until the last 15 seconds of the auction.

I also saw the "US Stock, ship by UPS, 100% original,..." but the other one says "Original Updatable Warranty" so what exactly does that mean? So, that's why I messaged them. These listings are just all over the place. We'll see if this seller replies to my question.

I do like diag-master's listing better than the rest of them but it seems like they all sell all of them and you could easily get a non-US model.

I'm sure I'm just not easy enough...

Thanks for the help!