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P2602




DTC P2600-P2603

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) 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 and cooling fan 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
* DTC P0111, P0112, P0113, P0116, P0117, P0118, P0119, P2600, P2602, or P2603 is not set.
* The ignition is OFF.
* The engine coolant temperature (ECT) at engine shut down is warmer than 110 °C (230 °F).
* The auxiliary coolant pump is enabled.
* The DTC runs continuously once the conditions above are met for greater than 30 seconds.

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 30 seconds.

P2601

The ECM detects that the ECT decreases less than 2 °C (4 °F) within 60 seconds. The condition exists for 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.

Diagnostic Aids

The auxiliary coolant or after boil pump relay may be referred to as "ENG PUMP" or "FUEL COOL" on the underhood electrical center (UBEC) cover label.

Reference Information
Schematic Reference

* Engine Cooling Schematics ([1][2]Cooling System)
* Engine Controls Schematics ([1][2]Electrical Diagrams)

Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Verify that DTCs P0480, P0481, P0691, P0692, P0693, and P0694 are not set.

• If a DTC is set, refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694 (w/LLT) (w/LLT)DTC P0480, P0481, P0691, P0692, P0693, or P0694 (w/LLT and Dual Fan) (w/LLT and Dual Fan) for further diagnosis.

2. Ignition ON, verify that the cooling fan or fans operate in all speeds.

• If the cooling fan or fans do not operate in all speeds, refer to Cooling Fan Inoperative (V6) (Cooling Fan Inoperative) for further diagnosis.

3. Ignition ON, command the KR31 auxiliary coolant pump relay ON and OFF with the scan tool. An audible click should be heard when changing between the commanded states.
4. Start the engine, observe the DTC information with a scan tool. DTCs P2600, P2602, or P2603 should not set.
5. 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 procedures for further diagnosis:

* 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)

6. 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

Note: The UBEC label may refer to this relay as the ENG PUMP or FUEL COOL relay.

1. Ignition OFF, disconnect the harness connector at the KR31 auxiliary coolant pump relay.

Note: 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.

Note: 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. Connect the red lead of the DMM to the KR31 relay control circuit terminal 86. Connect the black lead to ground. Set the DMM to the diode test setting. The DMM should display OL.

• If less than the specified range, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.

4. Command the auxiliary coolant pump relay ON and OFF with a scan tool. The DMM should transition from OL when commanded OFF to less than 1 V when commanded ON.

• If the circuit voltage does not correspond to the specified values, test the control circuit for an open/high resistance or for a short to voltage. If the circuit tests normal, replace the K20 ECM.

5. If all circuits/connections test normal, test or replace the KR31 auxiliary coolant pump relay.

Component Testing

Note: The UBEC label may refer to this relay as the ENG PUMP or FUEL COOL relay.

1. Ignition OFF, disconnect the auxiliary coolant pump relay.
2. Test for 70-110 ohm 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 A 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 ohm 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

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