The PCM provides ground to one side of the coil of the main relay and the other side is connected to the battery. The PCM monitors battery voltage and the voltage after the main relay.
Checking the contolling state of main relay every 10 sec. under detecting condition, if open or short in the circuit is detected for more than 5 sec., PCM sets P0685.
Item
Detecting Condition
Possible cause
DTC Strategy
? Detects a short to ground, to battery or open circuit on the main relay
? Poor Connection
? Open or short in control circuit.
? Faulty Main Relay
? Faulty PCM
Enable Conditions
? Engine Running
? 11V = Ignition Voltage = 16V
Threshold value
? Open or Short in circuit
Diagnosis Time
? Contineous (More than 5sec. failure for every 10 sec. test)
MIL On Condition
? DTC only (NO MIL ON)
If Main relay has a fault(ex. Open) under engine running, the DTCs,P0638/P0685/P1295/P2106, can happen at the same time.
- P0638 Throttle Actuator Control Range/Performance(Bank 1)
- P0685 PCM/PCM Power Relay Control Circuit /Open
- P1295 Throttle Actuator Control System - Power Management
- P2106 Throttle Actuator Control System - Forced Limited Power
Coil Resistance
70? ~ 120?