Gas

U0101-LOST COMMUNICATION WITH TCM

For a complete wiring diagram Refer to Diagrams/Electrical.


- When Monitored:
Ignition run time is greater than 1 second. Battery voltage between 9 and 16 volts. Engine run time greater than 3 seconds.

- Set Condition:
The PCM doesn't receive a Bus Message from the Transmission Control Module for 7 consecutive seconds. One trip failure. The circuit is continuously monitored. Two Trip fault.







Refer to the Communications test for this DTC and/or Manufacturer Code Charts for further possible causes.


Diagnostic Test


1. ACTIVE DTC
Start the engine.
With a scan tool, select View DTCs.

NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, because this fault is set after two failed trips.

Is the DTC Active or Pending at this time?

Yes


- Go To 2


No


- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition



2. PCM FUSED IGNITION SWITCH OUTPUT CIRCUIT




Turn the ignition off.
Disconnect the C1 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

With a 12-volt test light connected to ground and with special tool #8815 installed, probe the (F202), (F1), and (T751) Fused Ignition Switch Output circuit.
Perform the above check with the Ignition key in the off lock position, Ignition on, engine not running position, and during cranking.
Wiggle the related wire harness while probing the special tool with the test light to try to interrupt the circuit.
Does the test light illuminate brightly?

Yes


- Go To 3


No


- Repair the excessive resistance in the (F202), (F1), and (T751) Fused Ignition Switch (Off, Run, Start) circuit. Inspect the related fuse, if the fuse is open check the circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test



3. PCI BUS UNABLE TO COMMUNICATE WITH THE SCAN TOOL
NOTE: Determine which modules this vehicle is equipped with before beginning.

NOTE: When attempting to communicate with any of the modules on this vehicle, the scan tool will display 1 of 2 different communication errors: a NO RESPONSE message or a BUS +/- SIGNALS OPEN MESSAGE.

Ignition on, engine not running.
Use the scan tool, attempt to communicate with the remaining control modules.
Was the scan tool able to communicate with one or more of the Modules?

Yes


- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test


No


- Refer to the Communications test for this DTC and/or Manufacturer Code Charts for further possible causes.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test