Diagnostic Instructions

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

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Auxiliary Coolant Pump Relay Control	P2602	P2600	P2603	--
Ground	--	P2600	--	--

Typical Scan Tool Data

Aux. Coolant Pump Ckt. Short Gnd, Open, and Short Volts Test Status - Component Commanded OFF

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Component Commanded OFF Parameter Normal Range: The following illustrates the normal parameter state with no circuit conditions:     •  Component OFF - OK for Open/Short Gnd test and Not Run for Short to Volts test     •  Component ON - Not Run for Open/Short Gnd test and OK for Short to Volts test
Ignition Voltage	Fault	Fault	--
Auxiliary Coolant Pump Relay Control	Fault	Fault	Not Run

Aux. Coolant Pump Ckt. Short Gnd, Open, and Short Volts Test Status - Component Commanded ON

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Component Commanded ON Parameter Normal Range: The following illustrates the normal parameter state with no circuit conditions:     •  Component OFF - OK for Open/Short Gnd test and Not Run for Short to Volts test     •  Component ON - Not Run for Open/Short Gnd test and OK for Short to Volts test
Ignition Voltage	Not Run	Not Run	--
Auxiliary Coolant Pump Relay Control	Not Run	Not Run	Fault

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

P2601

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 Cooling Schematics

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References 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 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 for further diagnosis.

3. 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.
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 Inoperative

•	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

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 V 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 Ω 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 Ω between terminals 30 and 87 of the relay.

⇒	If greater than the specified range, replace the relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming