Fast Idle Lamp Circuit

TM 9-2320-312-24-2

Troubleshooting Section

i01606728

Fast Idle Lamp Circuit - Test

SMCS Code: 1900-081

System Operation Description:

Use this procedure under the following situation:

Personality Modules that have a Software Date

Code dated earlier than OCT01.

Use this procedure to determine if the fast idle lamp

(P1:31 output 9) is operating properly.

g00834354

Illustration 110

Output 9 can operate as a fast idle lamp or a wait

Schematic for the fast idle enable switch (OCT01 Option)

to start lamp. The "Output #9" parameter defaults to

"Fast Idle Lamp" and the ECM will turn on output 9

Test Step 1. Inspect Electrical Connectors

when the fast idle is active.

and Wiring.

Note: For "GM Truck Manufacturer" configurations,

the "Output #9" parameter is unavailable and output

9 functions as an output only for the fast idle lamp.

Electrical Connections of the Lamp

One terminal of the lamp must be connected to

battery voltage through the vehicle wiring. The other

terminal is connected to the ECM at the vehicle

harness connector P1:31.

The ECM provides a path to ground that will turn

on the lamp.

g00832955

Illustration 109

Schematic for the fast idle enable switch

OCT01 Software

OCT01 and newer Personality Module Software also

g00834349

Illustration 111

offers an alternative output that can be used for a

fast idle lamp. The parameter "Output #9" is not

Location of Output 8 and Output 9

used in the OCT01 software. The parameter "Fast

A. Thoroughly inspect ECM vehicle harness

Idle Lamp" has been added. "Fast Idle Lamp" can

connector J1/P1, the firewall bulkhead connector,

be programmed to "J1/P1:31" output 9, "J1/P1:21"

and the terminals for the fast idle lamp.

output 8, or "None".