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When I saw the mouse nest, I was actually happy - figuring I found the issue. However, even though there was a lot of debris on top of the tank, the wires looked to be untouched - no chewing anywhere between where the wire is not running through the interior of the car and the sending unit and my very (un)scientific test of wiggling the wires around in that area didn't seem to affect the car at all - How can I actually test that wiring and the sending unit?
@agent008 is part of the way there, but you also have to test the wires for short to ground, short to +12V and short to other wires. I have usually been able to visually inspect the wiring, looking for damage to it or to connectors.

Also, any advice on how to "test" the coils? I can pull the plugs easily enough and check them, though that would really be a head scratcher to have a bad plug and/or coil causing me a complete loss of power to the ignition system? Honestly, even a short on the fuel pump sending unit causing a loss of power on the ignition side would seem odd to me.
Normally, as @sahein stated, a bad coil will result in a misfire code, and that code is usually specific to a cylinder. Finding the bad component (coil, plug, injector, etc) generally involves switching components between cylinders and hoping the misfire switches to one of those cylinders. You don't have a misfire code, so that technique is not available to you.

Does anyone have a pinout diagram for the PCM connectors for a 2007 sky base?
Yes, I can post the ECM pinout tonight.
 
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I thin you are on track but there is one thing you mentioned early on and didn't extrapolate on.

You mentioned you had to replace the positive battery terminal lead and found corrosion on the terminal later as well as at the fuse box. Why did you have to replace the positive terminal lead, how was it damaged, and how did you replace it?

I ask because I had a Pontiac Grand Prix that did something like this. Sometimes hard starts...cut out while driving and wouldn't restart then would...etc. Turns out it was corrosion but the terminal looked fine. The corrosion worked down the positive lead and wound up corroding through the positive cable inside the insulation. You couldn't see it, couldn't feel it, and wasn't consistent. Replaced the whole positive lead and all was well.

I'm just wondering if when you remove the positive cable to reset things, if you aren't making the connection in the lead temporarily until it disconnects again. Just a theory to add to what you already have. This is a rough one.
 

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Discussion Starter · #64 ·
I thin you are on track but there is one thing you mentioned early on and didn't extrapolate on.

You mentioned you had to replace the positive battery terminal lead and found corrosion on the terminal later as well as at the fuse box. Why did you have to replace the positive terminal lead, how was it damaged, and how did you replace it?

I ask because I had a Pontiac Grand Prix that did something like this. Sometimes hard starts...cut out while driving and wouldn't restart then would...etc. Turns out it was corrosion but the terminal looked fine. The corrosion worked down the positive lead and wound up corroding through the positive cable inside the insulation. You couldn't see it, couldn't feel it, and wasn't consistent. Replaced the whole positive lead and all was well.

I'm just wondering if when you remove the positive cable to reset things, if you aren't making the connection in the lead temporarily until it disconnects again. Just a theory to add to what you already have. This is a rough one.
Robotech, Thanks for jumping in! For the positive cable, the factory connector snapped when I was tightening it back down (the little wedge piece directly under the nut), like your Grand Prix example, nothing in the positive cable gives any indication of any issues upon visual inspection. I will do a deeper check on that side. I don't know if it affects your theory or not, but when i disconnect the battery, i'm always doing it on the negative terminal side, I haven't touched the positive cable in a while.
 

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Discussion Starter · #65 ·
These are not a complete pinout but are relevant to the suspect areas as per your symptoms.
agent008,
Thanks for taking the time to post those, but do to my own inexperience I'm not sure how to read the diagrams? Do you know how I translate what's in the schematic to the actual ECM/PCM connector and Pin? I.e. if I wanted to trace the Camshaft position sensor - Exhaust, how do I know which connector to look at on the ECM and which pin? Also, do you have the schematics for the rest of the components in the ignition system?
 

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I'm on vacation at this moment so it isn't always easy for me to access my docs. You'll see the ECM pins labeled on the images as being contained within large dashed rectangles where it'll have a label, either X1 or X2. Each of these is one connector. Let us wait for others to help clarify which physical connector is X1 and which is X2.
 

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agent008,
Thanks for taking the time to post those, but do to my own inexperience I'm not sure how to read the diagrams? Do you know how I translate what's in the schematic to the actual ECM/PCM connector and Pin? I.e. if I wanted to trace the Camshaft position sensor - Exhaust, how do I know which connector to look at on the ECM and which pin? Also, do you have the schematics for the rest of the components in the ignition system?
This may help. Font Publication Parallel Paper Monochrome
 
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Discussion Starter · #68 · (Edited)
Another update: While messing around and scanning my car with a new scan tool that has GM specific software, so I could get BCM information - more on that later - I discovered with the key just in the Accessory position, my chattering relays almost stop - ALMOST. There was one relay that continued to actuate erratically, #26 the PWR TRN relay. So I think I'm getting closer here. This relay gets power with the key just in the Accessory position. Looking at the ecm pinout provided by #JohnWR the wiring diagrams from #agent008, and the Solstice wiring diagrams another member was kind enough to PM me, I'm still not sure how the power flows to actuate that relay. I.e. When I turn the ignition switch to ACC, can anyone explain what is involved in actuating that relay? Is it only the BCM, only the ECM, or are both modules involved? Any tips on what I need to do to test that circuit and how I can narrow this down? I'll replace both modules and the power distribution box if I have to, but I don't want to do that and end up in the same situation.

As for my new scan tool, a FOXWELL NT510Elite, initial impressions are that it's difficult to use, but does provide me with access to a lot more features than my basic obdII scanner. Including the ability to communicate with all the vehicle modules and run tests on individual circuits/relays. Last evening when I did a full scan, I got the following information that i really cannot rely on, since i had been removing fuses and relays over the last couple of months and probably caused at least some of these. Note that I was able to communicate with the ECM, and then I wasn't - does this communication go through the BCM first?

I'll clear them all and start fresh this week and see if I get codes that lead me in one direction:
Fault CodeStatusDescription
U2105_001.Last test:Failed/current 2.This ignition:Not ran 3.Since cleared: Passed HistoryLost communications with ECM
B3265_061.Last test: Passed 2.This ignition: Passed 3.Since cleared: Passed HistoryTrunk release output circuit short to
ground/open
B1325_031.Last test: 2.Since cleared:Device power 1 circuit low voltage
B0081_711.Last test: Passed 2.This ignition: Passed 3.Since cleared: Passed historyPassenger presence system 1
invalid serial data received
B1370_061.Last test: Passed 2.This ignition: Passed 3.Since
cleared: Passed history
Device ignition 1 circuit short to
Ground
U2103_001.Last test: Passed 2.This ignition: Passed 3.Since cleared: Passed historyFewer controllers on bus than
programmed

Thanks again for everyone's input, this is truly an awesome forum!
 

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Fault CodeStatusDescription
U2105_001.Last test:Failed/current 2.This ignition:Not ran 3.Since cleared: Passed HistoryLost communications with ECM
B3265_061.Last test: Passed 2.This ignition: Passed 3.Since cleared: Passed HistoryTrunk release output circuit short to
ground/open
B1325_031.Last test: 2.Since cleared:Device power 1 circuit low voltage
B0081_711.Last test: Passed 2.This ignition: Passed 3.Since cleared: Passed historyPassenger presence system 1
invalid serial data received
B1370_061.Last test: Passed 2.This ignition: Passed 3.Since
cleared: Passed history
Device ignition 1 circuit short to
Ground
U2103_001.Last test: Passed 2.This ignition: Passed 3.Since cleared: Passed historyFewer controllers on bus than
programmed
Your relay chatter and the short to ground + low voltage errors still point to a wiring or battery or grounding issue.

You might want to read the following thread from the Solstice Forum, it would be worth checking your fusible link if it's OK.

Let's see what other experienced members can suggest.
 

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You might want to read the following thread from the Solstice Forum, it would be worth checking your fusible link if it's OK.
Sorry, I referenced the wrong thread. It's this one
 

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Maybe this is over-simplified, maybe you tried it already. Have you changed relays? Maybe the ones making noise are semi-failed.

I also support the idea of a compromised ground connection.
 

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Discussion Starter · #72 ·
Maybe this is over-simplified, maybe you tried it already. Have you changed relays? Maybe the ones making noise are semi-failed.
I also support the idea of a compromised ground connection.
rjgramps, thanks for the comment! I have not actually gotten any new relays. However, I have "swapped" relays, and I have a relay tester, that is telling me the relays are functioning appropriately. Like you, an issue with a ground was my first thought, and since I haven't solved the problem, I cannot say that's not the issue. However, I have checked and cleaned ground connections in the following locations: Front of engine, back of the engine, front right and left frame connections, frame connection under the battery, frame connection in the cabin by the emergency brake. I'm trying to narrow down where I have to check, now that I know the manifestation of intermittent, inconsistent power seems to occur with the key just in the ACC position, and I know it's affecting the PWR TRN relay, I am trying to extensively examine all circuitry/wiring that is involved in that operation (Including all grounds involved), which is the reason for my last inquiry.
 

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Have you checked your 12v voltage in different points of the car. Ie. between both battery posts, then between battery positive and engine ground. Between battery positive and some other grounds. Check the voltage on the relay that's chattering.
Just some ideas...
 

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....... Note that I was able to communicate with the ECM, and then I wasn't - does this communication go through the BCM first?
.......
The high-speed LAN is a two-wire daisy-chain network, and an interruption in any part of it will disable the car.

Physically, the wiring goes:
  1. DLC (Data Link Connector)
  2. Data Link Resistor
  3. BCM (Body Control Module)
  4. VCIM (Vehicle Communication Interface Module) (OnStar, if fitted)
  5. EBCM (Electronic Brake Control Module)
  6. TCM (Transmission Control Module) (If automatic transmission is fitted)
  7. ECM (Engine Control Module)
 
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Discussion Starter · #75 ·
The high-speed LAN is a two-wire daisy-chain network, and an interruption in any part of it will disable the car.

Physically, the wiring goes:
  1. DLC (Data Link Connector)
  2. Data Link Resistor
  3. BCM (Body Control Module)
  4. VCIM (Vehicle Communication Interface Module) (OnStar, if fitted)
  5. EBCM (Electronic Brake Control Module)
  6. TCM (Transmission Control Module) (If automatic transmission is fitted)
  7. ECM (Engine Control Module)
OK, so over the weekend I didn't get a chance to do as much as i wanted. I did remove and inspect the rear connector on the BCM - it looked pristine, no evidence of any corrosion or wire issues. I also checked the voltage directly at the alternator - with the car running normally - and I saw it at 14.4. At the same time, at the battery terminals, i was seeing 14.2V and 14.3 at the starter. To me those small voltage differences to not seem significant, but just wanted to check here on my understanding/interpretation?

I'm still waiting to replace the ECM - working on seeing if I can get it replaced under warranty. In the mean time, what are the chances this issue is within the OnStar module? I keep coming back to the thought that this has to be a computer module issue, just because every time i disconnect the battery and reconnect it, it will make the car run normally for some (inconsistent) amount of time. I just cannot see how that behavior could be attributed to a short or open ground? I mean it's seemingly unrelated to the ambient temperature, to the engine temperature, how long it's running/how long it's sitting. The only consistent behavior is, disconnect the power source, re-connect the power source - vehicle changes behavior. As an IT professional, this leads me back to the computer world, where you can resolve all kinds of issues with a reboot, and sometimes when that's not enough, removing the power source and waiting 30 seconds resolves it. Just rambling here, as I'm just hoping it comes to me (either through divine intervention and/or someone on this forum) .
 

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Discussion Starter · #76 · (Edited)
Update: I finally replaced the ECM. However, after discovering the warranty terms were less than favorable, decided to just buy a replacement from Ebay for $109. One thing on the warranty was "If we find the module not defective upon our inspection, I would have had to pay them $80 + return shipping.

Anyway, I'm cautiously optimistic that my issue is resolved, though only time will tell. It starts fine and I didn't have to do any security relearn.

As for my scanner the, Foxwell NT510 elite, it has the crankshaft relearn function listed however, I was only able to initiate the test one time and the scanner froze in the middle. Every other time I attempted to use that function I get an error "Device limits exceeded".
UPDATE: I successfully got the relearn procedure to work. The scanner tells me Not to put the emergency brake on and only tells me to apply the brake when starting. Apparently the instructions are wrong. I had to start the car with the brake and keep the brake applied for the procedure to work (instructions I followed found here: Cel Code P0315 on dashhawk.)

I will update in a week or two if I don't have any more issues, otherwise, I'll update this thread when the issue returns. Thanks again for everyone's help on this!
 
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