V1 Gremlins - multiple symptoms SOLVED

[escapepilot]

Which one are you calling the start relay coil?

The one on the Starting/Charging diagram labeled Starter Relay Coil Control in the PCM, C1 pin 48. Circuit 447. I get nothing on that wire. No voltage, no continuity to ground. On the right side of that diagram is a relay that only shows the line and load side but there isn't a clear picture where the signal to close that relay comes from so I'm guessing it's related. Honestly, at this point, I'm grasping, but at least grasping in a smaller pile now.

 

[Gtstorey]

That's not a wake up control, that's what will actually activate the crank relay to activate the starter solenoid to cause it to crank. It's almost the last link in the chain and is controlled by the ECM (grounded) when all of it's condition are met. I'm pretty sure that the lack of 5v on pin 6 if the ignition switch is part of the problem but I don't know if its the cause or a symptom.

Does the security light come on with key on? I think it should as a check of the bulb just like the check engine light comes on with key on.

 

[Gtstorey]

Can someone review the power distribution (figure 3) from post 28 and confirm my reading on what the voltage should be at each pin based upon key position? I know that we aren't seeing 5V on pin 6, but if we were does this match?

I'm also starting to wonder if maybe the 5v is supposed to be hot all of the time, even though it's in a "logic"box. Otherwise I'm not sure how the "key in" could do anything.

 

[escapepilot]

That's not a wake up control, that's what will actually activate the crank relay to activate the starter solenoid to cause it to crank. It's almost the last link in the chain and is controlled by the ECM (grounded) when all of it's condition are met. I'm pretty sure that the lack of 5v on pin 6 if the ignition switch is part of the problem but I don't know if its the cause or a symptom.

That is what I was thinking but don’t know where the wake up signal woul come from unless it comes through the data wires. There is no separate wire from BCM to that circuit that I can find.

Does the security light come on with key on? I think it should as a check of the bulb just like the check engine light comes on with key on.

It did, but it is not now. At first I was thinking the TDM, but am getting proper signals out at each pin.

 

[Gtstorey]

That is what I was thinking but don’t know where the wake up signal woul come from unless it comes through the data wires. There is no separate wire from BCM to that circuit that I can find.
There is no wake up to a relay. Once the tdm, bcm, and ECM all agree then the ECM will ground the relay.

It did, but it is not now. At first I was thinking the TDM, but am getting proper signals out at each pin.

There is no wake up to a relay. Once the tdm, bcm, and ECM all agree then the ECM will ground the relay.

You are leaving out the data logic.

 

[escapepilot]

There is no wake up to a relay. Once the tdm, bcm, and ECM all agree then the ECM will ground the relay.

You are leaving out the data logic.

Not trying to leave it out, just don’t know where it comes from since it’s not laid out in a diagram that I can follow. Thanks for your help. I definitely would be stuck.

 

[Gtstorey]

It comes from the computer in the module. It’s getting beyond what I fully understand but it sends “data” in packets over the data wires that the appropriate module can interpret. It’s hard to tell what that data is without an appropriate scanner. So all you can do is confirm that everything is getting appropriate power and ground without the scanner.

 

[Gtstorey]

I can PM you my phone number if it will help you to talk it through.

 

[Gtstorey]

Just for the heck of it, I combined my interpolation of the wiring diagram in post 43 with the power mode table from the later model service manual (post 33) and it looks like it would pretty much match up. Not totally sure about the exact voltages that should be on pin 5 since they might have changed the resistor and it isn't labeled in the older diagrams.

And maybe I'm extrapolating to far and it doesn't mean anything. But it looks to me like the lack of 5v on pin 6 is a problem. But again I can't tell if this is a symptom of something else or the main problem. About the only way I can come up with to get a final answer is to have a scanner that will read everything.

I might have time this weekend to check if I get the 5v at pin 6 with the TDM unplugged. That might help determine if a problem with the TDM is causing your issue. But it would probably be better if someone with an older model checked.

I could also loan you my tech2 windows clone, but no guarantee that you will be able to get it to work. I have to play with it for an hour every time I use it updating things and remembering how to set it up. And it may just run with older windows and computers since I think it is supposed to only work on 64bit computers.

 

[Gtstorey]

I also just checked and the older diagram labels in the "logic" box in the BCM pretty much match the newer labels except for ignition1-run/crank.

 

[escapepilot]

Our internet went out at work this morning with no idea when it will come back up so I took a half day and am going to get back on this after lunch.

 

[escapepilot]

Well…the garage gnomes must have came and worked their magic last night. Before I start diagnosing, I always try it to see what happens since it is an intermittent problem. Key to Run = everything comes alive. So left it that way and checked the 5v circuit from BCM to ignition and, yep, 4.4v as it should be. Pulled the crank relay and checked and the circuit that was giving me trouble - the one from the PCM to the Crank Relay coil side = ground when key to Start.

So…I feel pretty good stating the problem is in that 5v logic circuit. Question is why. Is it internal to the BCM or is there some ground wire. I feel like I can see the light at the end of the tunnel.

 

[Gtstorey]

Where exactly did you measure the 4.4v?

Have you ever backprobed BCM C2-62 when it wouldn't crank?

There are 5 possible failures for the BCM not putting out the 5V signal.
1. Logic: Something is telling the BCM to not turn it on.
2. Transformer failure in the BCM.
3. The BCM has several different connections for +v and ground. The transformer will likely use one pair of these and we don't know which pair it is or what/if anything else may use that pair. So a loose connection on one of these could be a problem. These are likely pins on the back of the BCM (large connectors).
4. The 5v is available at the BCM and it is a lost connection between the BCM and switch. These small pin BCM connectors are hard to check and may just need something adding extra pressure holding down the connector. Or a broken wire.
5. The 5v wire is shorting to ground between the BCM and switch.

Intermittent problem probably counts out number 2, although not 100%. Maybe the transformer gets hot and stops working. Letting it set gives it a chance to cool down and start working again. You can probably test this if it starts after sitting overnight.

My guess is #4. When it will start, you need to carefully wiggle the connectors and see if you can make it not work.

 

[Gtstorey]

Another thought. If there are any other 5v reference circuits output by the BCM they may be supplied by the same transformer (actually been reading, it might be a "chip" that steps it down) and they are grounded, it will pull the whole circuit down to 0. Is the cruise control or maybe the brake/clutch switch working off 5v? I might would expect something as important as starting to have it's own 5v supply, but maybe not.

 

[escapepilot]

BCM C2-62 is where I’m getting the 4.4x volts and it was back probed.

#3 I did check all wires on the back BCM C4 connector. Everything checked ok. I did not load test the grounds though. There is only the one main ground on the BCM (C4 E12) and two signal grounds C1-61 and C1-64 (not used, no pin in connector on LSJ).

#4 I checked the connectors at the ignition switch. When it wasn’t working, neither pin 5 white nor pin 6 white/black had voltage but while it is working, I have proper voltage at both pins.

#2 the last two times it has failed it has remained in a failed state across multiple days so probably does rule out a transformer.

#5 I didn’t have voltage back probing the BCM connector on either pin when it was in a failed state.

I also tested the TDM. With Key on and everything working, unpluged the TDM and had no change.

 

[escapepilot]

Another thought. If there are any other 5v reference circuits output by the BCM they may be supplied by the same transformer (actually been reading, it might be a "chip" that steps it down) and they are grounded, it will pull the whole circuit down to 0. Is the cruise control or maybe the brake/clutch switch working off 5v? I might would expect something as important as starting to have it's own 5v supply, but maybe not.

The only other 5v circuits are at the PCM and go to the various engine sensors.

 

[Gtstorey]

So 5v works when the TDM is unplugged?

It's starting to sound like either the BCM is bad or the pin C2-62 is making an intermittent connection to the BCM. Not sure how to tell which it is.

I wonder if the odometer reset was done like this: Resetting the Odometer - How To | DF Kit Car Forum
If so they may have damaged something inside the BCM.

 

[escapepilot]

Feel confident it’s internal to the BCM. A replacement is on the way. Replacing the BCM is easy but not cheap. Tracking a broken wire is cheap but not easy. I I’ve already spent so many hours chasing this problem that I don’t want to spend that time unless absolutely necessary.

 

[Gtstorey]

Did you order new/preprogrammed or used?

 

[escapepilot]

Used. Local shop buys enough that he gets a warranty with it. He also has the info from mine already backed up so he can match the VIN and everything.