P2601
DTC P2600-P2603
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptors
DTC P2600
- Auxiliary Coolant Pump Relay Control Circuit
DTC P2601
- Auxiliary Coolant Pump Performance
DTC P2602
- Auxiliary Coolant Pump Relay Control Circuit Low Voltage
DTC P2603
- Auxiliary Coolant Pump Relay Control Circuit High Voltage
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The auxiliary coolant pump system provides a measure of prevention against fuel vaporization due to excessive engine temperatures. The engine control module (ECM) commands the auxiliary or after boil coolant pump ON when the engine coolant temperature exceeds a calibrated value after engine shut down. The ECM applies ground to the coil side of the auxiliary pump relay. This energizes the coil and applies voltage directly to the pump motor through the switch side of the relay.
Conditions for Running the DTC
P2600, P2602, or P2603
* The engine speed is greater than 80 RPM.
* The ignition voltage is between 10-18 volts.
* The ECM has commanded the pump ON and OFF at least once during the ignition cycle.
* The DTCs run continuously once the above conditions are met.
P2601
* DTCs P0111, P0112, P0113, P0116, P0117, P0118, P0119, P02600, P02602, and P02603 are not set.
* The engine coolant temperature at shut down is greater than 110 °C (230 °F) for longer than 70 seconds.
* The DTC run continuously once the above conditions are met.
Conditions for Setting the DTC
P2600
The ECM detects the pump control circuit is open. The condition exists for 4 seconds or a cumulative of 50 seconds.
P2601
The ECM detects the engine coolant temperature remains greater than 110 °C (230 °F) for more than 4 seconds or a cumulative of 30 seconds.
P2602
The ECM detects the pump control circuit is shorted to ground. The condition exists for 4 seconds or a cumulative of 30 seconds.
P2603
The ECM detects the pump control circuit is shorted to voltage. The condition exists for 4 seconds or a cumulative of 30 seconds.
Action Taken When the DTC Sets
The DTCs are Type C DTCs.
Conditions for Clearing the DTC
The DTCs are Type C DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, command the auxiliary coolant pump relay ON and OFF with the scan tool. An audible click should be heard when changing between the commanded states.
2. Start the engine, observe the DTC information with a scan tool. DTCs P2600, P2602, or P2603 should not set.
3. Ignition ON, engine off observe the DTC information with a scan tool. DTC P2601 should not set.
• If DTC P2601 is set refer to the following links:
* After Boil Coolant Pump Always On (After Boil Coolant Pump Always On)
* After Boil Coolant Pump Inoperative (After Boil Coolant Pump Inoperative)
* After Boil Coolant Pump Malfunction (After Boil Coolant Pump Malfunction)
4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the auxiliary coolant pump relay.
Important: The ignition circuit supplies voltage to other components. Make sure you test all circuits for a short to ground or test all components for being shorted that share the ignition circuit.
2. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal 85 and ground.
• If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition voltage circuit fuse is open, test all components connected to the ignition voltage circuit and replace as necessary.
Important: The control circuit for the auxiliary coolant pump relay is pulled-up to voltage within the ECM, 2.6-4.6 volts on the control circuit is normal.
3. Test for 2.6-4.6 volts between the control circuit terminal 86 and ground.
• If less than the specified range, test the control circuit for an open/high resistance or for a short to ground. If the circuit tests normal, replace the ECM.
• If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Connect a test lamp between the control circuit terminal 86 and the ignition voltage circuit terminal 85.
5. Command the auxiliary coolant pump relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always OFF, replace the ECM.
6. If all circuits/connections test normal, test or replace the auxiliary coolant pump relay.
Component Testing
1. Ignition OFF, disconnect the auxiliary coolant pump relay.
2. Test for 70-110 ohms between terminals 85 and 86.
• If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If not the specified value, replace the relay.
4. Connect a 20-amp fused jumper wire from the positive terminal of the battery to relay terminal 85. Connect a jumper wire from the negative terminal of the battery to relay terminal 86. Measure for less than 2 ohms between terminals 30 and 87 of the relay.
• If greater than the specified range, replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Control Module References (Programming and Relearning) for ECM replacement, setup, and programming