Chart 4

Diagnostic Chart:

Schematic:

The PCM contains an Output Driver Module (ODM) which controls the air pump relay coil circuit ground. The ODM monitors the feedback voltage level on circuit 436 at the PCM when the device is being commanded On or Off. When the device is commanded Off (circuit not grounded), the voltage level at the PCM should be high (ignition voltage). When the device is commanded On (circuit grounded), the voltage level at the PCM should be low. Chart 4 diagnoses a high circuit voltage fault in which the PCM detected higher than normal feedback voltage when the air pump relay was commanded On.

DTC PARAMETERS
DTC P1640 will set if air pump relay feedback voltage is greater than 3.5 volts when air pump relay is commanded On when:
^ Condition exists for longer than 6 seconds
^ Engine is running

DTC P1640 diagnostic runs continuously with engine running.

P1640 is a (type C) DTC

DIAGNOSTIC AIDS
To locate an intermittent problem, use Scan to command AIR PUMP RELAY On while monitoring AIR PUMP REL. CKT SHORT TO VOLTS. When a fault (short to voltage or shorted solenoid) exists, the Scan tool will display YES.

Air pump realy coil resistance: 70-115 ohms