P159C

DTC P159C

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.



DTC Descriptor
DTC P159C
- Power Take-Off (PTO) Remote Engine Shutdown Switch Circuit




Diagnostic Fault Information






Circuit/System Description

The power take-off (PTO) is an upfitter integrated system that allows the user to create an auxiliary power source. The PTO system specifically controls engine speed to values higher than normal base idle, PTO load relay engagement, and remote starting and shutdown of the engine. When the operator requests PTO using either the PTO switch or PTO remote, the engine RPM will increase to a default standby speed. The engine control module (ECM) converts the data from the engine speed sensor to a 2 pulses/engine revolution signal. When PTO is engaged, the power take-off module (PTOM) sends a GMLAN serial data message to the ECM requesting engine speeds, in accordance with the depressed switches from the PTO switch or remote.


Conditions for Running the DTC

The engine is running and PTO is engaged.


Conditions for Setting the DTC

* The PTOM detects a signal mismatch between the remote engine shut off signal and the PTO engine shutdown signal.
* The above condition is present for greater than a predetermined time threshold.



Action Taken When the DTC Sets

* The PTOM stores the DTC information into memory when this diagnostic runs and fails.
* The malfunction indicator lamp (MIL) will not illuminate.
* PTO becomes disabled until the next ignition cycle.
* The remote engine start function defaults back to disabled.



Conditions for Clearing the DTC

* A last test failed, or the current DTC, clears when the diagnostic runs and does not fail.
* A history DTC clears after 40 consecutive warm-up cycles, if failure is no longer present.



Reference Information
Schematic Reference

Power Take-Off (PTO) Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views
Description and Operation

Power Take-Off (PTO) Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information


Circuit/System Verification

With PTO enabled, momentarily press the remote engine shutdown switch. The engine should shut down.


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the PTO module.
2. Connect a test lamp between the signal circuit terminal 31 and ground.
3. Ignition ON, command the PTO remote engine shutdown using the upfitted remote engine shutdown switch. The test lamp should turn ON as the switch is depressed and OFF as the switch is released.

• If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, test or replace the upfitted remote engine shutdown switch.


• If the test lamp is always OFF, test the remote engine shutdown switch supply voltage circuit and the signal circuit for a short to ground or an open/high resistance. If both circuits test normal, test or replace the upfitted remote engine shutdown switch.

4. If all circuits test normal, replace the PTO module.



Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


Control Module References for PTO module replacement, setup, and programming