Table C-1B A/C Idle-Up Circuit Check

Idle-Up Circuit Check:

Idle-Up Circuit Check:

Circuit Description

When the A/C compressor clutch is in operation, the A/C amplifier will send an A/C idle-up signal to the Powertrain Control Module (PCM). The PCM sends a signal to the Idle Speed Control (ISC) motor. This signal to the ISC motor will activate a plunger to open the throttle plate. As the throttle plate opens, the engine idle speed increases to prevent a rough idle or stalling condition.


Diagnostic Aids

An intermittent malfunction, may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Check for the following items:

^ Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections before component replacement.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. Checks for an increase in Idle speed with the A/C "ON."

3. With the A/C "ON" (operating) the A/C Idle up signal circuit at the PCM should indicate 0V.

4. With the A/C "OFF" (not operating) the A/C Idle up signal circuit at the PCM should indicate B+.

6. With the A/C "OFF" (not operating) the A/C cut-out signal circuit at the PCM should indicate 0V.

7. With the A/C "ON" (operating) the A/C cut-out signal circuit at the PCM should indicate B+.