1994 PCED OBDI-A
SECTION 18A: Diesel Diagnosis — 7.3L DI Engine
AB: Injector Driver Circuit Operation
Introduction
  AB: Pinpoint Tests  





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 CID and provide regulated current to the unit injectors, based on FDCS from the IDM internal 115V supply. The injection timing and duration is commanded by the PCM in the FDCS signal.

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

The IDM (injector drive module) 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 test will also allow the operator to enable all injector solenoids while the engine is off to verify circuit operation. IDM detected diagnostic trouble codes will not be transmitted if the EF line is not functioning; however, the engine will function normally.

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. 





Note

After removing connectors always check for damaged pins, corrosion, loose terminals, etc.



Engine Harness Connector Check to Chassis Ground
Test PointsSpec.ActualComments
B>10,000 ohms Injector low side
C>10,000 ohms Injector power feed, high side
D>10,000 ohms Injector low side



Valve Cover Gasket Connector to Chassis Ground
(Check with pigtail connector installed on gasket connector)
Test PointsSpec.ActualComments
B>10,000 ohms Injector low side
C>10,000 ohms Injector power feed, high side (120 volts when engine is running)
D>10,000 ohms Injector low side



Under Valve Cover Harness and Injector Solenoid Resistance Checks
(Check with pigtail connector installed on gasket connector)
Test PointsSpec.ActualComments
B to C2 to 4 ohms Resistance through injector solenoid and UVC harness
C to D2 to 4 ohms Resistance through injector solenoid and UVC harness



Engine Harness to IDM Connector Checks
Test PointsSpec.ActualComments
Cylinder 1
B to 6		<5 ohms Injector low side
Right Side
C to 24		<5 ohms Injector powerfeed, high side (120 volts when engine is running)
Cylinder 3
D to 21		<5 ohms Injector low side
Cylinder 5
B to 8		<5 ohms Injector low side
Right Side
C to 24		<5 ohms Injector powerfeed, high side (120 volts when engine is running)
Cylinder 7
D to 20		<5 ohms Injector low side
Cylinder 2
B to 22		<5 ohms Injector low side
Left Side
C to 23		<5 ohms Injector power feed, high side (120 volts when engine is running)
Cylinder 4
D to 7		<5 ohms Injector low side
Cylinder 6
B to 19		<5 ohms Injector low side
Left Side
C to 23		<5 ohms Injector power feed, high side (120 volts when engine is running)
Cylinder 8
D to 9		<5 ohms Injector low side

 

 

  AB: Pinpoint Tests