P2600

Diagnostic Chart:

Schematic:

The auxiliary coolant pump is located underhood near the center front of dash. One of its two functions is to maintain constant engine coolant flow to the heater core whenever engine speed is between idle and 1800 rpm with the engine coolant temperature (ECT) between 0 and 81°C (32 and 178°F). The second function of the auxiliary coolant pump is to prevent engine coolant boilover after the engine has been turned Off with the ECT greater than 104°C (229°F). The pump will run from 4 minutes at 104°C (219°F) up to 5 minutes at 120°C (248°F) with the engine Off (ignition On or Off). The ECM controls the auxiliary coolant pump by supplying a ground to the auxiliary coolant pump relay coil control circuit. When the auxiliary coolant pump relay is commanded Off, the voltage at the ECM should be high (ignition voltage). When the auxiliary coolant pump relay is commanded On, the voltage at the ECM should be low. The ECM auxiliary coolant pump relay feedback circuit uses a pull-up voltage (2.6-4.6 volts), which allows the ECM to individually differentiate between an open, short to ground or short to voltage. DTC P2600 will set if the ECM detects an open auxiliary coolant pump relay control circuit when auxiliary coolant pump relay is commanded Off with engine cranking/running.

DTC PARAMETERS
DTC P2600 will set if auxiliary coolant pump relay feedback voltage is between 2.6 and 4.6 volts (ECM pull-up voltage indicating an open circuit) when auxiliary coolant pump relay is commanded Off when:
^ Condition exists for longer than 0.5 seconds
^ Engine speed is greater than 40 rpm
^ Main relay voltage is between 8.0 and 18.0 volts

DTC P2600 diagnostic runs continuously once the above conditions have been met.

P2600 is a type D DTC.

DIAGNOSTIC AIDS
To locate an intermittent problem, use Scan tool to monitor DTC P2600 LAST TEST with engine running above 1800 rpm OR ECT above 81°C (178°F). Wiggling wires while watching for a change from PASSED to FAILED may locate the area where an open in the wiring may exist.

Auxiliary coolant pump relay coil resistance: 70-115 ohms