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 P061C 00: Control Module Engine Speed PerformanceCircuit/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.
Conditions for Setting the DTC
| • | The PTOM detects that the requested RPM and the actual engine RPM do not match. |
| • | 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.
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. |
Diagnostic Aids
| • | When not in mobile PTO mode, heavy engine load may cause this code to be set. |
| • | Use a scan tool to observe the PTO inhibit and disengage history. |
Reference Information
Schematic Reference
Power Take-Off (PTO) Schematics
Connector End View Reference
Power Take-Off (PTO) Connector End Views
Description and Operation
Power Take-Off (PTO) Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
Engine ON, press 1 on the PTO switch to engage PTO. The engine RPM should increase to the default engine speed within a few seconds. Press RES + to increase the engine speed and SET - to decrease the engine speed accordingly.
Circuit/System Testing
Important:
• Repair any ECM related DTCs or symptoms before using this diagnostic. • This DTC may be stored as a history DTC without affecting the operation of the ECM or PTOM. Do not replace the ECM or PTOM if this DTC is stored only as a history DTC and is not retrieved as a current DTC.
- Engine ON, clear codes in the PTOM and then engage PTO. Verify that DTC P061C does not reset as current in the PTOM.
- If all circuits test normal, refer to Diagnostic Aids. Do not replace the PTOM.
| ⇒ | If the specified code sets as current, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for ECM replacement, setup, and programming
