Test Step 4. Check ECM Operation of the Fast Idle Lamp

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TM 9-2320-312-24-2

Troubleshooting Section

Test Step 4. Check ECM Operation of the

Note: For OCT01 and newer Personality Module

Fast Idle Lamp.

Software, insert the jumper into P1:31 or P1:21. The

terminal location depends on the programming of

the "Fast Idle Lamp" parameter.

E. Connect the other end of the jumper wire to

P1:65 (-battery).

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

G. While the lamp is being watched, insert the

jumper wire and remove the jumper wire.

Expected Result:

Result 1 The fast idle lamp turns on while the

jumper is connected to both sockets. Also, the fast

idle lamp turns off when the jumper is removed from

one of the sockets.

Result 2 The fast idle lamp does not turn on while

the jumper is connected to both sockets.

Result 3 The fast idle lamp will stay on while the

g00834353

Illustration 113

ECM vehicle harness connector is disconnected.

Pin locations on the Breakout T

Results:

A. Disconnect ECM vehicle harness connector

J1/P1.

Result 1 The fast idle lamp is functioning

properly. Proceed to Test Step 4.

B. Insert a breakout T between ECM vehicle

harness connector J1 and ECM vehicle harness

Result 2 The fast idle lamp did not turn on. The

connector P1.

vehicle's lamp circuit is not functioning properly.

The lamp is probably burned out or there is a

C. Connect one probe of the voltage test lamp to

problem in the wiring from the cab to either the

P1:65 (-battery). Connect the other probe of the

ECM or the +battery connection. Repair the lamp

voltage test lamp to P1:52 (unswitched +battery)

circuit or send the vehicle to the OEM dealer for

of the breakout T.

repairs. STOP.

D. The test lamp should turn on. If the test lamp

Result 3

does not turn on, either the test lamp is faulty or

the wiring to the ECM is faulty. Continue with this

Repair: Perform the following diagnostic

step if the lamp turns on.

procedure:

E. Leave the probe of the test lamp connected to

The circuit between the ECM and the lamp is

P1:52 (unswitched +battery).

shorted to chassis ground. Repair the circuit or

send the vehicle to the OEM dealer for repairs.

F. Connect the other probe of the test lamp to

P1:31 (output 9) of the breakout T.

STOP.

Refer to Illustration 113.

G. Connect an ET. Access the following display

screens in order:

Diagnostics

Diagnostic Test

Special Test