Test Step 3. Test the Lamp Circuit -807640352

174

TM 9-2320-312-24-2

Troubleshooting Section

Test Step 3. Test the Lamp Circuit.

g00676968

Illustration 47

Result 2 The lamp did not turn on. The vehicle's

A. Disconnect ECM vehicle harness connector

J1/P1.

lamp circuit is not functioning properly. The lamp

is probably burned out or there is a problem in

B. Fabricate a jumper wire 100 mm (4 inch) long.

the wiring from the cab to either the ECM or the

Crimp a Deutsch Pin to both ends of the wire.

+Battery connection. Repair the lamp circuit or

send the vehicle to the OEM dealer for repairs.

C. Insert the jumper into the terminal 28 (check

STOP.

engine lamp) of connector P1.

Result 3

D. Connect the other side of the jumper wire to P1

terminal 65 (-battery).

Repair: Perform the following diagnostic

procedure:

E. Turn the ignition key switch to the ON position.

The circuit between the ECM and the lamp is

F. While the lamp is being watched, insert the

shorted to chassis ground. Repair the circuit or

jumper wire and remove the jumper wire.

send the vehicle to the OEM dealer for repairs.

Refer to Illustration 47.

STOP.

Expected Result:

Result 1 The check engine lamp turns on while

the jumper is connected to both sockets. Also, the

check engine lamp turns off when the jumper is

removed from one of the sockets.

Result 2 The check engine lamp does not turn on

while the jumper is connected to both sockets.

Result 3 The lamp will stay on while the ECM

vehicle harness connector is disconnected.

Results:

Result 1 The check engine lamp circuit is

functioning properly. Proceed to test step 4.