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2004 Chevrolet Silverado CAN

Scott Owner California Posted Latest

Question

Delayed

Driveability

2004 Chevrolet Silverado 3500 6.6L (2 LLY) 5-spd (1000) — 1GCJC33204F265840

U0073 — Control Module Communication Bus "A" Off

U0100 — Lost Communication With ECM/PCM "A"

U0101 — Lost Communication with TCM

P0700 — Transmission Control System (MIL Request),

MIL On

Hi All,

The above mentioned truck was towed in as a no-start, won't crank a while back. The client drove the vehicle until it wouldn't run anymore. The turbo broke the clamp holding the turbo together. The resulting damage was a result of the turbo coming apart.

What was noticed initially were the following DTC's -

Transmission/TCM, U1016 Lost Communication With The Powertrain/Engine Control Module (PCM/ECM), U0073 Lost Communication With The High Speed CAN Communication Bus, U0100 Lost Communication With Engine ControlModule (ECM)

The Body Control Module (BCM) had these DTC's stored:, U1000 Class 2 Data Fault, U1096 Lost Communication With The Instrument Panel Cluster (IPC), U1009 No DTC description for this - see PIT3793, B2550 Backup Lamps Control Circuit

There was no communication with the ECM on the vehicle initially and the engine wouldn't crank.

Parts replaced were the engine wire harness, turbo, A/C hose (suction), PCV hose assembly, heater hoses…When I went to start this the engine did not crank and there was no communication from the ECM. The TCM communicated. At the UBEC the EDU/IGN 1 Relay was not turning on and the ECMRPV and EDU fuses were not powering up. A replacement ECM was installed and programmed. GM part - …

The vehicle starts and runs now, but…The wait to start lamp will just stay on. The ECM now has a P0700 and U0101 Lost Communication With Transmission Control Module (TCM) and the TCM has the U0073 and a U0100 Lost Communication With Engine Control Module (ECM) and the MIL is on.

If I'm reading this correctly GM wants you to start with U0073 which states - A total non-communication condition is detected on the CAN serial data circuit. The FICM, GPCM, TCM, and ECM are on the CAN bus. I went to the GPCM with a DMM and saw 2.45 v and 2.25 v. This a scope pattern, I've never looked at this before, but it appears normal?

diag.net/file/fde76xgto…

Here's the file.

diag.net/file/f5htp5kgi…

GM says to disconnect CAN circuits 2361 and 2362 starting with the FICM. Does this reset? If it does then disconnect CAN from the GPCM, then the TCM, then the ECM. All this is easier said than done. I guess if I have to I can back the terminals out, but I wondered if someone had some other thoughts.

Danny Technician

Wisconsin

Danny

Here in the midwest i'm always looking at the under hood fusebox for corrosion.

Ð Awarded

Agree

Dmitriy Analyst

Ontario

Dmitriy

A waveform like this may happen if there is extra resistance somewhere on the bus – just enough to make the transmission not reliable. Can be wiring, can be inside connectors. It might be noticeable by using an ohmmeter on the unpowered bus. If you want to check if any two modules (for example, ECM and TCM) have good wiring between them, put two scope channels on one, the other two channels on…

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Helpful

Agree

Scott Owner

California

Scott

Hi Dmitriy, I appreciate the reply. So you’re saying this is not a normal pattern for this particular bus. Would you happen to have what it should look like? Could this have anything to do with how the settings were set up on my capture? Thanks

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Ryan Owner/Technician

British Columbia

Ryan

Yes, your time base is quite long and you have a low sample rate effecting your capture. Both CAN high and low appear to be base lining slightly low at 2.3 volts in your capture. I have attached a known good CAN from the GPCM on a 2004 LLY Duramax which is at 2.5 volts.

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Helpful

Dmitriy Analyst

Ontario

Dmitriy

Scott, there are packets with different voltages in the waveform, as if they are shifted relative to each other. They are a little bit hard to see because of the low sample rate, this is why I proposed the experiment with two channels on each suspect module, and a higher sample rate. diag.net/file/f5ynlr15j…

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Thanks

Todd Diagnostician

Michigan

Todd

This is just a private CAN network with only one connector in the circuits. I'd check the terminals in the large connector on the left valve cover, if that's OK I'd check your grounds. G102, G108 and G109. Left and right side of block near front.

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Ray Diagnostician

Ontario

Ray

Another method to ck for resistance in the communication circuits, is to get a small bulb with the socket and the pigtail. First, connect the pigtail across the battery terminals and measure the amp draw, lets say 2 amps. Disconnect the connector from one of the modules and connect fused power and ground to the 2 comm wires. On the other module, disconnect the connector and connect the bulb…

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Matt Educator

Ohio

Matt

Are those codes current or history? Can you communicate to the ECM and TCM with your scan tool? Just a nice to know, if the TCM is the module with the porcupine heat sink on the back, I have seen failures with them.

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Scott Owner

California

Scott Delay

Hi All, This one is currently on hold. Adding to the story above, was the customer had contacted his insurance company and they agreed to the repairs seen at that point. The adjuster sent out an inspector for State Farm and when he initially looked at this he mentions the insulator on the firewall and a few other items that I did not include on the original estimate. State Farm sent over an…

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