Computer and Output Circuits
Diagnostic Codes: P1607, P1621, P1622MIL Output Circuit, P1607
A hardware testis carried out on the MIL Lamp by the engine control module (ECM). The instrument pack "bulb-check" period, after the ignition is switched on, is used to drive the MIL Lamp ON and OFF for a period of time. This allows the diagnosis of open and short circuit faults. Two successive trips within which the diagnostic indicates a fault will lead to a fault being stored.
Monitoring Procedure
The bulb check period, after the ignition has been switched on, is used by the MIL Lamp manager to drive the MIL Lamp both ON and OFF, which allows the hardware to diagnose both open and short circuits.
The strategy will report to the Diagnostic Status Manager (DSM) when a MIL Lamp monitoring fault is present and the DSM will then decide whether to store a fault code and illuminate the MIL Lamp.
Possible Causes:
- Wiring / connector fault in MIL Lamp harness
- Body computer to GEMS harness connector - open circuit or short circuit
- GEMS ECM hardware monitor faulty
ECM Engine Immobilization In put Circuit Malfunction, P1621
A range check on the diagnostic L-line is performed to check for voltages outside expected limits. On detecting out of range voltages the appropriate fault code is stored and MIL lamp illuminated.
Engine Immobilization Input Code Malfunction, P1622
With the ignition ON, and the security system "disarmed" the security ECM transmits the appropriate authorization code to the ECM. If the ECM receives two identical incorrect; or three different incorrect; authorization codes from the security ECM; then this will be interpreted as an illegal attempt to start the vehicle.
On detection of an illegal attempt to start the vehicle, a fault code will be stored and the MIL Lamp illuminated.