Injector Driver Circuit Operation

1997 PCED OBDII-Diesel

SECTION 5C: Pinpoint Tests

AB: Injector Driver Circuit Operation
Introduction

Output Functions

High Side Drive Outputs (Right and Left Bank) — The high side driver output function is to distribute energy to the proper bank based on cylinder identification (CID) and provide regulated current to the unit injectors, based on fuel delivery command signal (FDCS) from the injector driver module (IDM) internal 115v supply. The injection timing and duration is commanded by the powertrain control module (PCM) in the FDCS.

Low Side Drive Outputs — The low side drive outputs control the sequencing (firing order) of the engine based on the CID and FDCS inputs.

WARNING: RED-STRIPED WIRES CARRY 115V DC. SEVERE ELECTRICAL SHOCK MAY BE RECEIVED. DO NOT PIERCE.

CAUTION: Do not pierce engine electrical wires or damage to the harness may occur.

Detection/Management

Note: Special instructions required to clear IDM trouble codes (1995/1996 model year).

Key on.
Record IDM trouble codes stored in KOEO ON-DEMAND SELF TEST and KOEO INJECTOR ELECTRICAL SELF TEST modes.
Access RETRIEVE/CLEAR CONTINUOUS DTCs from NGS Tester menu to clear IDM trouble codes from memory.
Record any codes displayed. (P1111 may be the only code displayed.)
Push CLEAR ALL button on NGS Tester.
IDM trouble codes are now cleared from memory. Repeat the KOEO On-Demand Self Test and KOEO Injector Electrical Self Test. Any IDM codes that reappear are IDM hard faults. If no IDM codes reappear, then the fault is an intermittent IDM fault.

The IDM is capable of detecting individual injector open and shorts to either ground or battery while the engine is running. It is also capable of detecting right or left bank high side opens or shorts to ground. A special on-demand buzz electrical self test will also allow the operator to enable all injector solenoids while the engine is off to verify circuit operation. IDM detected trouble codes will not be transmitted if the EF line is not functioning; however, the engine will not shut down due to a non-functional EF line.

If a low side short to ground condition is determined by the IDM, this condition will be transmitted to the PCM via the EF signal. The PCM will enable the CHECK ENGINE light and command minimum fuel to the affected bank.

AB: Pinpoint Tests