2007 Equinox 3.4 U0131 No Comm to Pwr Steering

I had cleared all the codes night before last, drive to work yesterday morning and scanned it after I arrived - all clear. I scanned it again after I got home and it was still all clear. When I scanned it after getting to work this morning I saw a U0131 BCM lost communication with Power Steering Control Module.

I found three places on the Internet where they're talking about a reprogram is required, one article is on iATN and I don't have a subscription and cannot get one since I am a DIY; one article is on AllData but I do not have a subscription currently for the Equinox and the third article is on Chevrolet Workshop Manuals.

I went to Mitchell and logged into my subscription for the Equinox and cannot find anything about a Reprogramming Campaign on there in the TSBs. Searching for U0131 only brings up a description of the code but no help as to what to do about it. How do you guys approach communication errors? There was a slew of these things before I cleared the codes two days ago so something is amiss.

Thanks in advance,
Gary

Well start with checking all fuses and grounds ....

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Any dash lights, or power steering issues when this code set? Just wondering if there's any other symptoms associated with the code.

I looked at the iATN TechHelp you linked, it ended in BCM replacement. BUT, they also had other stuff going on, like door locks cycling, lights going out, traction control indicator illuminating, like that. That Chevy workshop manuals TSB you found might be on the right track, but only if you're actually losing power steering at the same time.

Here's a quick glance at the network topology:



At first glance, I don't suspect a wiring issue at all. If there were some kind of open between the BCM and PSCM, then you'd be getting loss-of-com codes in other modules further down the line (ECM, EBCM, ect.). Same for a short.

Ben & Tyler,

I had just gone through all of the grounds and all of the fuses are good. The BCM was just replaced about two months ago, it only has about 400 miles in it, for what that is worth. Just for good measure, though they tested good, I disconnected the battery and pulled the two main ground wires off, one was on the block and there is an eyelet leading right from the PCM, I shined it up a bit and coated it in dielectric grease, and did the same to the one that is just beside the battery attached to the inner fenderwell. I had read about some issues with fretting at the 80 Amp Mega fuse so I did the same with it.

I put a multimeter across pins 6 & 14 on the DLC and wiggled the connector at each point starting at the power steering module, then I'd disconnect the plug and make sure the resistance rose to 120Ω, I worked my way from module to module to each end of the network, ending at the EOL resistor near the fuel tank and then at the PCM which serves as the EOL resistor on the opposite end, the ABS module plug moved the DMM some so I disconnected it and sprayed contact cleaner in the plug and reconnected it. The passenger airbag still won't come on and driving it 20 miles produced yet another friggin P0300 code.

On a side note, after I did the code scan on the OE side I looked at the OBD side, in the Health Check and "Pending" and there it was, then I went to OBD Direct and looked in Mode 3 Display Trouble Codes and there was nothing there, but, in Mode 7 Display DTCs Detected During Last Drive, there it was. So for what it's worth, I know a bit more about how the GM/SnapOn Pending codes work now. If nothing else, this car sure serves as a good bad example...

Gary

I checked alldata and mitchell neither had any info on the code or a flow chart to diagnose it ... not that we'd use those anyways! Lol man this car is torture it seems like every other day there's something new with it .... what a pain oh well you sure are getting some good training on it . What did you find with the 0300 were you logging any miss fires or have any in history? Maybe time for a carbon clean I swear by the motorvac machine. do you have a scope? interested to see what secondary ignition looks like make sure those batter cables are clean and the feed wire to fuse box corrosion plays heck with the modules ...

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Yes Ben, I've got 281 misfires on Cylinder 2, 50 to 90 on the others. I do have a scope, secondary ignition looks pretty good, but I'm new at this. The waveforms look great until I snap the throttle, then there is a little hash but very little, based on watching Paul's videos, it didn't look abnormal. I looked at the primary current ramps too and they also look good. I want to do an injector balance test but the frickin test won't run, I get an error saying the Fuel Enable Flag Not Set or somesuch. I don't know why, Tyler gave me some things to try but it refuses to play ball. The injectors are buried beneath the intake, of course... I can pull the plug on the PCM and do it that way with my injector tester but I was hoping to not have to do that. The connectors are 90 degree so I can't just backprobe them.

It's all so intermittent, seems like if it were restricted injectors I wouldn't be able to drive for a day and a half with nary a code and then have it suddenly fall apart the next day. That is why I was looking so closely at the module connections and ground wires.

The battery cables are perfectly clean, surprisingly clean for a 10 year old, they look nearly new. This thing is kicking my ass for sure. It's my daughter's car, she needs to sell it, they totally emptied their savings to buy another car because this is unusable for them, and all of us are totally opposed to unloading this thing to some unsuspecting person; we all want to get it working right before we sell it.

Gary

Tyler wrote: Any dash lights, or power steering issues when this code set? Just wondering if there's any other symptoms associated with the code.

I looked at the iATN TechHelp you linked, it ended in BCM replacement. BUT, they also had other stuff going on, like door locks cycling, lights going out, traction control indicator illuminating, like that. That Chevy workshop manuals TSB you found might be on the right track, but only if you're actually losing power steering at the same time.
At first glance, I don't suspect a wiring issue at all. If there were some kind of open between the BCM and PSCM, then you'd be getting loss-of-com codes in other modules further down the line (ECM, EBCM, ect.). Same for a short.

Tyler, I failed to answer part of your questions, no power steering issues at all, dash lights, sort of, I get that "Stabilitrak Off" traction control (disable, whatever it says) message at times, normally it's so sensitive that even a pending code will shut it down.

Three other oddities, one is an intermittent very long crank, normally it fires up within a second but when it does this long-crank thing, it takes many seconds to start and then it often idles rough for a sort time. The second one is surging, sometimes it's really noticeable even at highway speeds but usually it's when I'm driving like 30mph and the thrid one is hesitation. But, these are all intermittent.

Gary

When you scoped the secondary did you check the peak kv on each wire and compare? If #2 has a much higher kv you could have a wire issue or gap to big or a broken plug if kv is to low the gap is likely to small if your fire line is short and kv jumps nearly as high as your fire line than it may be a severely fouled plug here's a shot of the last 0300 I dealt with this was very obvious when I put the scope on this cylinder I wish they were all this easy
If you notice I'm set to 20 kv and I'm going over that which is to high for idle and the end of the spark line which is half as long as it should be jumps to around 12kv which is way to high! This 1 ended up being a severely fouled plug with a ton of buildup on it...

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Ben,

Thanks for the good information, I will rerun the test and record all of the results and post them, I'll try to get some screenshots too. I replaced the plugs and wires about 6 months ago but I don't put much stock in whether a part is new or not, my Dad taught me long ago that new does not always equate to good.

I cleared all of the codes again this morning and noticed the battery voltage was only 11.5 volts, it barely started... so much for having the battery drain issue sorted. Holy cow, I can't catch a break on this thing. It seems like it behaves a little differently each time I have the battery disconnected. I went back through some old stuff I had made note of when I had the use of a Verus last fall. I saw that the BCM reported a ROM error on the ECM, interesting. I attached the file, it appears nears the top of page 4.

With all the erratic stuff I am starting to think the ECM may be bad, the BCM was and has been replaced. Part of why I say that is this morning I was watching the misfire monitors in the OE side. What I saw was unexpected. No misfires in the first page, which for my Solus is the current stuff and reset upon the Misfire Cycle rolling over from 99 to 0 and begins again, but, on the next or Misfire History page, they were counting up AND RESETTING... wth??!! I watched this go on for about 20 minutes. Once I got off the highway and to a stop light I stopped communication, disconnected the scan tool, unplugged it and shut it down, restarted it, plugged it in, re-initiated a new session and watched it a while longer. It worked properly for about three minutes and went right back to the previous behavior.

I arrived at work about five minutes later and switched to the OBD side and went to Mode 6 (I think that is right, maybe it's Mode 7) and looked at the misfire data and it had been counting up for each cylinder.

What are your thoughts on this?

<edit> the file will not attach, I've tried six times to no avail

Gary

Well I'm not sure what it is but all of these gm sport utilities have been plagued with electrical issues....

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Was the bcm a new or used unit?

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I just read your last post on the drain Do you need a ground location diagram I can pull 1 up later and post it if needed?

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Here's the diagram for c3 connector on bcm I glanced at the other connectors and didn't see anything relevant let me know if you need anything else

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Ben,

The BCM was new hopefully, I didn't know what was wrong with the car at the time, it would take about 20 minutes after reconnecting the battery before it would come up to a point where you had dash lights and it would seem like it was going to crank but it never would. It was towed to a local shop that was recommended to my son-in-law by his friend who is an instructor at a local auto college, similar to Rosedale. The ignition lock cylinder was damaged and we all believed that it would require removing the airbag to replace it and the school apparently won't do that so they recommended the local shop.

Thanks for the wiring diagram, I did not know that the BCM was grounded behind the kick panel!! There is a ground point right beneath it, G203 and I naively assumed that is where the BCM would be grounded, lesson learned... I will go and check it out next.




I'm trying again to attach the old report from the Verus I has use of last fall.

Also, I scoped the ignition again last night and it looks good, I compared it to my Toyota Tacoma that was sitting next to, they look pretty much the same. I'm using a borrowed Pico, I saved some of the data.

Gary

doesn't look like it attached that file, I don't know why this won't work

What format is it? You can email it to me and I can try to upload it for you .

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I think that I would start looking at Powers and grounds. GM has a lot of Ignition switch and power distribution problems.

Gary B wrote: Tyler, I failed to answer part of your questions, no power steering issues at all, dash lights, sort of, I get that "Stabilitrak Off" traction control (disable, whatever it says) message at times, normally it's so sensitive that even a pending code will shut it down.

Three other oddities, one is an intermittent very long crank, normally it fires up within a second but when it does this long-crank thing, it takes many seconds to start and then it often idles rough for a sort time. The second one is surging, sometimes it's really noticeable even at highway speeds but usually it's when I'm driving like 30mph and the thrid one is hesitation. But, these are all intermittent.

Gary

Yeah, the Stabilitrak will usually take any excuse it can to shut off. "Oh, it's a full moon? Nope, I'm out!" :silly:

Any chance you've taken a look at the P0300 freeze frame? Just trying to connect ambient temperature, cold/hot soak time, or engine load to your misfire.

The long crank time and rough idle... Has the throttle body been cleaned recently? It might sound weird, but these engines will start hard and idle like crap with a dirty throttle. I dunno that the throttle will account for your misfire, but I think it's highly suspect on your long crank time.

I agree the throttle body is always worth cleaning for a hard start . A good motorvac carbon clean may be in order to cure those few miss fires

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