SOLVED! No Crank, No Start, Communication Codes Present

[cope1980]

Hi Guys, I'm back again with another issue. Y'all were a great help on my last problem, Thanks for being here.

I've got a 2004 GMC Envoy XUV 4.2L SLT. It is our daily driver and only vehicle, so I am desperate to resolve my problem.

I'm sorry if this is a long read, I want to try to provide as much info as possible.

Codes:
B0780 Control Unit 1A
B0775 Control Unit 1A
B0770 Control Unit 1A
U1000 Control Unit 1A
U1064 Control Unit 1A
U1041 Control Unit 1A
U1000 Control Unit 58
U1064 Control Unit 10

History of this issue:

A few days ago, I got in to start the car, and no crank. The display read "UNKNOWN DRIVER" and "TAILGATE AJAR". Security light was on. Windows would not roll down and dome lights would not come on. I Checked battery voltage (12.65v) and all of the fuses. Everything there was fine. I did the Passlock relearn process and did not solve it. I removed the neg battery cable for 30 minutes or so, and when I reconnected it, the car was able to start.

Yesterday, My wife parked at the store, and turned the car off. When she tried to star the car, she said the security light was on, display read "UNKNOWN DRIVER" and "TAILGATE AJAR", the doors were locking and unlocking repeatedly, windows would not roll down and car would not crank. Then the horn started honking. She pushed the horn button on the key fob and got it to stop. After about 10 minutes the car started fine.

Today, the car again has no crank, same display messages, no windows, no locks. I pulled the codes with a cheap ELM327 adapter and a phone app. I have tested the starter relay socket, and checked/cleaned the BCM ribbon cable. I bypassed the Passlock sensor with a resistor.

What I have done:

Checked Battery Voltage
Performed Passlock relearn
Checked Fuses, visually and with ohm meter
Removed neg battery cable
Tested voltages at starter relay socket (as per instructions found on here)
Removed, checked and cleaned BCM ribbon cable to rear distribution box
Bypassed Passlock with resistor as per South Main Auto video found on here


Thanks in advance, Billy

 

[TJBaker57]

I bypassed the Passlock sensor with a resistor

what value resistor and where/how is it connected? security
relearn done afterwards? (I don't really watch videos)

Was your drivers door module ever replaced under the warranty for 2004 vehicles?

Do you use Torque Pro?

 

[cope1980]

I measured 9.06k ohms during crank. I used a 100k and 10k resister in parallel. I used an ohm meter to check the resistance. It was 9.1k. I cut the yellow passlock wire, one end of parallel resistor soldered to BCM side of yellow wire, opposite end was soldered into black passlock wire. Key side of yellow wire was heat shrinked as a dead termination. resistor and solder connections were covered with heat shrink. I did the connections on the underside of the column, to the left side of the ignition switch. Yes, I did the relearn. I am actuall re running it right now.

Unsure about the module replacement. We have only owned it for 5 years.

I currently use Car Scanner, but I can download Torque

 

[TJBaker57]

Hi Guys, I'm back again with another issue. Y'all were a great help on my last problem, Thanks for being here.

I've got a 2004 GMC Envoy XUV 4.2L SLT. It is our daily driver and only vehicle, so I am desperate to resolve my problem.

I'm sorry if this is a long read, I want to try to provide as much info as possible.

Codes:
B0780 Control Unit 1A
B0775 Control Unit 1A
B0770 Control Unit 1A
U1000 Control Unit 1A
U1064 Control Unit 1A
U1041 Control Unit 1A
U1000 Control Unit 58
U1064 Control Unit 10

History of this issue:

A few days ago, I got in to start the car, and no crank. The display read "UNKNOWN DRIVER" and "TAILGATE AJAR". Security light was on. Windows would not roll down and dome lights would not come on. I Checked battery voltage (12.65v) and all of the fuses. Everything there was fine. I did the Passlock relearn process and did not solve it. I removed the neg battery cable for 30 minutes or so, and when I reconnected it, the car was able to start.

Yesterday, My wife parked at the store, and turned the car off. When she tried to star the car, she said the security light was on, display read "UNKNOWN DRIVER" and "TAILGATE AJAR", the doors were locking and unlocking repeatedly, windows would not roll down and car would not crank. Then the horn started honking. She pushed the horn button on the key fob and got it to stop. After about 10 minutes the car started fine.

Today, the car again has no crank, same display messages, no windows, no locks. I pulled the codes with a cheap ELM327 adapter and a phone app. I have tested the starter relay socket, and checked/cleaned the BCM ribbon cable. I bypassed the Passlock sensor with a resistor.

What I have done:

Checked Battery Voltage
Performed Passlock relearn
Checked Fuses, visually and with ohm meter
Removed neg battery cable
Tested voltages at starter relay socket (as per instructions found on here)
Removed, checked and cleaned BCM ribbon cable to rear distribution box
Bypassed Passlock with resistor as per South Main Auto video found on here


Thanks in advance, Billy

The U1064 from the PCM (control module 10) is the primary issue. The PCM is losing communications with the body control module (BCM).

 

[TJBaker57]

I currently use Car Scanner, but I can download Torque

I also have Car Scanner but it hasn't got a good terminal mode. here is a free serial terminal we can use.

https://play.google.com/store/apps/details?id=de.kai_morich.serial_bluetooth_terminal

With this we can ask all modules in the vehicle to respond and we can see if the BCM is active or not.

I will post the instructions when you get the app installed

 

[cope1980]

Ok, how or where do I start checking? I am Mechanically and electrically inclined, but the data stuff is WAYYYY over my head.

 

[cope1980]

App is installed and open

 

[TJBaker57]

measured 9.06k ohms during crank. I used a 100k and 10k resister in parallel. I used an ohm meter to check the resistance. It was 9.1k. I cut the yellow passlock wire, one end of parallel resistor soldered to BCM side of yellow wire, opposite end was soldered into black passlock wire. Key side of yellow wire was heat shrinked as a dead termination. resistor and solder connections were covered with heat shrink. I did the connections on the underside of the column, to the left side of the ignition switch. Yes, I did the relearn. I am actuall re running it right now.

I never watched the video but knowing how the system works that sounds about right. Personally I don't do such modifications I just fix the issue. But it should work.

 

[cope1980]

Ok, I have the app open and it is connected to OBDII

 

[TJBaker57]

App is installed and open

OK. We need to do some simple setup.

App is installed and open

Top left menu,,

In settings, "receive", set to CR.

In settings, "send", set 'clear input on send'

Top left menu again, select devices and choose your OBDII.

App should connect.to your ELM device

Key ON

at the bottom enter one line at a time...

ATTP2
ATAL
ATH1
ATS1
ATSH6CFEF1
20
20
20


Each line that starts with AT is a configuration command for the ELM, does not send to vehicle.

Each line should get an "OK" response.

Each "20" sent should yield a bunch of responses.

 

[TJBaker57]

The result should look something like this, but with more responses

 

[cope1980]

All of the At's responded with "OK"
The 20's responded like yours, but with different numbers

 

[TJBaker57]

What we are looking for is in the third byte in the responses. This is the node address of the the module that is replying. The one we are looking for is "40", that is the BCM. We want to know is the BCM alive on the network.

Off the top of my head here are some of them.

10 =PCM
1A = TCCM
29 = EBCM
40 = BCM
58 = SIR
60 = IPC
80 = RADIO
98 = HVAC

 

[cope1980]

I see all of those except 40.

I also see a few not listed.

 

[Mooseman]

Pardon the interruption, just an observation.

Your combination of codes and UNKNOWN DRIVER sure sounds a lot like this one:

Unknown Driver?

I have a deposit on a super clean 2002 Bravada with 130000 miles. I went and test drove it yesterday. First I hooked up my Equus 3130. The truck runs very warm, a good 1/8" past the 210 mark on the gauge. The live data reads 220-225F. My 2002 Envoy would never get that warm. It appears to have...

gmtnation.com

The U1064 points to an issue with the DIM (dash integration module), which I believe is part of the BCM. And with the missing response from the BCM, sounds like an issue with the BCM.

 

[TJBaker57]

I see all of those except 40.

I also see a few not listed.

Yes, there will be others

But what is important is we do not see 40. So the BCM is not there. The BCM does all the vehicle security and Passlovk stuff so without the BCM you are going nowhere.

So we have either a BCM that does not have the power it needs or a bad ground or the serial data line is compromised.

 

[cope1980]

Pardon the interruption, just an observation.

Your combination of codes and UNKNOWN DRIVER sure sounds a lot like this one:

Unknown Driver?

I have a deposit on a super clean 2002 Bravada with 130000 miles. I went and test drove it yesterday. First I hooked up my Equus 3130. The truck runs very warm, a good 1/8" past the 210 mark on the gauge. The live data reads 220-225F. My 2002 Envoy would never get that warm. It appears to have...

gmtnation.com

The U1064 points to an issue with the DIM (dash integration module), which I believe is part of the BCM. And with the missing response from the BCM, sounds like an issue with the BCM.

I suspect the BCM, and have questioned it from the beginning of this issue. That's why I checked, cleaned the ribbon cable. I did not want to start shotgunning parts, without knowing for sure.

 

[TJBaker57]

Under the hood, fuse TBC1 fuse 31. Test for power there. This is the main BCM power supply. Power without a ground does nothing so we need to look up where the BCM grounds to also.

 

[TJBaker57]

The BCM grounds at the ribbon cable from a ground on the lower left B pillar. At the ribbon cable the grounds are at A11 and B11. You should be able to test one of these without disconnecting anything. There are small metal points at the point the ribbon cable goes into the connector. You can test there.

 

[cope1980]

Under the hood, fuse TBC1 fuse 31. Test for power there. This is the main BCM power supply. Power without a ground does nothing so we need to look up where the BCM grounds to also.

I just tested fuse 31 with vom. It is good. I checked both sides to ground.

 

[cope1980]

The BCM grounds at the ribbon cable from a ground on the lower left B pillar. At the ribbon cable the grounds are at A11 and B11. You should be able to test one of these without disconnecting anything. There are small metal points at the point the ribbon cable goes into the connector. You can test there.

A11 has ground and B11 has ground. Tested from the ribbon contact to the Pos feed to distribution box.

 

[TJBaker57]

Have a look here, tell us if you have one or both lf these wires. At the BCM

 

[TJBaker57]

Have you checked fuses in the rear fuseblock? Specifically TBC2, TBC3, TBC4, TBC5.

 

[cope1980]

I just see one of them.

I have, but I will test them again now

 

[TJBaker57]

You can also keep trying that "20" in the serial terminal app while checking the tightness of connectors and fuses etc. Look for that "40" in the responses.

By your description of the truck working then not working we are dealing with an intermittent issue here. Maybe a dirty connection or loose fuse socket.

 

[TJBaker57]

I just see one of them.

I have, but I will test them again now

All of the fuses I mentioned send power to the BCM at all times. I do not know which ones are required for the BCM to operate and which are for other resources that the BCM controls

 

[TJBaker57]

I just see one of them.

I have, but I will test them again now

Ok on the one wire..... early models had a redundant serial data line from BCM to PCM bypassing the data splice pack that is in the left dash.

 

[cope1980]

You can also keep trying that "20" in the serial terminal app while checking the tightness of connectors and fuses etc. Look for that "40" in the responses.

By your description of the truck working then not working we are dealing with an intermittent issue here. Maybe a dirty connection or loose fuse socket.

I rechecked the fuses, all ok.

I wiggled wires and plugs in various places and gave the distribution box a couple of whacks with my hand. Still no 40.

 

[TJBaker57]

Back at the picture I posted with the serial data wires.

Right under the "s" in the word "serial" is an orange wire. That is the power from fuse 31 under the hood. Use a pin or something to probe in there and test for 12 volt power there.

 

[cope1980]

Back at the picture I posted with the serial data wires.

Right under the "s" in the word "serial" is an orange wire. That is the power from fuse 31 under the hood. Use a pin or something to probe in there and test for 12 volt power there.

Yes there is power there

 

[TJBaker57]

Do you have access to that resistor you put in still? I am thinking of trying to find a way to determine if the BCM is powering up OK. If the BCM has the power and ground it needs then when the key is turned to RUN there should be 5 volts or so coming from the BCM on that yellow wire that you connected to one end of your resistor pair.


The other possibility is there is an issue with that one serial data wire you have. That wire runs to a splice pack under the left dash where most all the modules are connected together.aybe the BCM is alive but the serial data line is hosed.

 

[cope1980]

Yes, I can access the resistor. I'll check it and look at the splice pack now

 

[cope1980]

Do you have access to that resistor you put in still? I am thinking of trying to find a way to determine if the BCM is powering up OK. If the BCM has the power and ground it needs then when the key is turned to RUN there should be 5 volts or so coming from the BCM on that yellow wire that you connected to one end of your resistor pair.


The other possibility is there is an issue with that one serial data wire you have. That wire runs to a splice pack under the left dash where most all the modules are connected together.aybe the BCM is alive but the serial data line is hosed.

Zero Volts at the resistor with key in run position

 

[cope1980]

I am not sure what I am looking for, but I did find a large connector under the column. I also located a 2 amp ATO fuse under the column. There is no voltage on either side of the fuse to ground, however when I measured from positive on the ignition switch to each side of the fuse, I did read ground. Not sure if that is relevant.

 

[TJBaker57]

Zero Volts at the resistor with key in run position

This at the very least suggests the BCM is NOT powering up OK.

So likely NOT a serial data wire issue.

We need to verify all the powers at the BCM.

Ribbon cable terminals:
A1, B4, B13, B17 should have 12 volts hot at all times, even at key off.

 

[cope1980]

This at the very least suggests the BCM is NOT powering up OK.

So likely NOT a serial data wire issue.

We need to verify all the powers at the BCM.

Ribbon cable terminals:
A1, B4, B13, B17 should have 12 volts hot at all times, even at key off.

All of them have 12 v with key off

 

[cope1980]

Would it hurt or help if I remove the BCM and look for broken pins or solder connections?
Also check the J plugs?

 

[TJBaker57]

With key to ACC terminal A18 should go hot and in that state there should be about 5 volts going to the yellow wire that connects to your resistor pair.

I have a setup in a drawer here that operates with just those 5 hot at all times terminals hot, two grounds and the A18 terminal and I have my passlock voltage (yellow wire) at 4.92.

 

[TJBaker57]

If you have a verified ground at A11, & B11, and power to the 5 hot at all times terminal we checked. And then apply power at terminal A18 (that comes from the ignition switch to ACC, RUN and Start) and there is still no 5 volts to the yellow Passlock wire then it is looking like a BCM fault. In this case it could be time to remove and inspect the BCM for obvious damage. The BCM case opens up real easy to inspect the circuit card.

 

[cope1980]

With key to ACC terminal A18 should go hot and in that state there should be about 5 volts going to the yellow wire that connects to your resistor pair.

I have a setup in a drawer here that operates with just those 5 hot at all times terminals hot, two grounds and the A18 terminal and I have my passlock voltage (yellow wire) at 4.92.

A18 0 volts key OFF
A18 12v key to ACC
0 volts at yellow passlock with key at ACC