Models Produced From March 1990

Series Resistors (MPI Engine Management System):

When the ignition is turned ON, battery power is applied to a series resistor pack where it then branches out through 5 individual resistors (one for each injector). Power from the series resistor pack then goes to the individual injectors at their #2 terminals. Each injector is energized individually when the ECU completes that circuit to ground.

CAUTION: These injectors are very low impedance and must be used with a resistor in series with each injector. Applying battery power and ground directly to an injector will damage the injector.

CHECKING USING SELF DIAGNOSTIC OUTPUT CHECK

1. Perform output check, call up codes 4411 through 4421. Output Diagnostic Test Mode (DTM)

If any one injector fails to operate, check for:

a. Poor connection, corrosion or damaged terminals at injector.
b. Open or grounded circuit between injector harness connector terminal #2 and its respective terminal on series resistor pack connector.
c. Open circuit between injector harness connector terminal #1 and its respective ECU terminal.
d. Faulty resistor in resistor pack. Check resistance between resistor pack grey connector terminal #1 and each of the remaining terminals on both connectors. Resistance should be 5.0-8.0 ohms for each measurement. If any one measurement is outside of the specified range, replace resistor pack.
e. Open or shorted injector. Check resistance between terminals on injector in question. Resistance should be 1-3 ohms. If not, replace injector.

Series Resistor Pack Connectors Terminal ID:

Injectors are connected to resistor pack and ECU terminals as listed below.

RESISTOR PACK GREY CONNECTOR
Terminal #1 - power supply from fuse #13.
Terminal #2 - injector cyl. #1 - ECU terminal 4D.
Terminal #3 - injector cyl. #2 - ECU terminal 5D.
.
RESISTOR PACK BROWN CONNECTOR
Terminal #1 - injector cyl. #3 - ECU terminal 6D.
Terminal #2 - injector cyl. #4 - ECU terminal 9D.
Terminal #3 - injector cyl. #5 - ECU terminal 10D.


If no wiring problems are found and injector has power at its #2 terminal but still will not operate, check all ECU power supply and ground circuits. Repair as necessary. If no problems are found, then the ECU is faulty.

If all five injectors fail to operate, check for:

a. Fuse #13 blown.
b. Open circuit in wiring between series resistor pack grey connector terminal #1 (Grn/Y wire) and fuse #13.
c. Open circuit between fuse #13 and terminal 52/87 of fuel pump relay.
d. Faulty fuel pump relay.

Repair as necessary.

If no wiring problems are found and injectors have power at their #2 terminals but still will not operate, check all ECU power supply and ground circuits. Repair as necessary. If no problems are found, then the ECU is faulty.