Inspection Procedure

DTC 51 - Switch Condition Signal

PROCEDURE
1. CHECK OUTPUT CONDITION OF DTC 51.
- To set the diagnosis system to the Test mode.
- Turn ignition switch OFF.
- Connect terminals TE2 and E1 of data link connector 2 (DLC 2).
- Turn ignition switch ON. (For checking terminal IDL, disconnect the vacuum hose from the throttle body, then apply vacuum to the throttle opener)
- Connect terminals TE1 and E1 of DLC 2.
- Check if code "51" is output by the malfunction indicator lamp:

Park/Neutral Position Switch (PNP)
P or N position: Normal Code.
R, D, 2 or L position: Code 51.

Throttle Position Sensor (IDL)
Accelerator pedal released: Normal Code.
Accelerator pedal depressed: Code 51.

A/C Switch (A/C)
A/C SW OFF: Normal Code.
A/C SW ON: Code 51.

NOTE: DTC 42 is output with vehicle speed 3 mph or below.

- If OK proceed to "Diagnosis By Symptom".
- If not OK (PNP switch circuit) refer to PNP switch circuit diagnosis.
- If not OK (A/C switch circuit) proceed to step 3.
- If not OK (throttle position sensor IDL circuit) proceed to step 2.

2. CHECK RESISTANCE OF THROTTLE POSITION SENSOR.
- Disconnect throttle position sensor connector.
- Disconnect the vacuum hose from the throttle body, then apply vacuum to the throttle opener.



- Measure resistance between terminals 2 (IDL) and 1 (E2) of throttle position sensor connector.

Throttle Valve
Fully closed: Less than 2-3 k Ohms.
Opened: 1 M Ohms or higher.

- If OK Check and repair harness or connector between ECM and throttle position sensor.
- If not OK adjust or replace throttle position sensor.

3. DISCONNECT A/C AMPLIFIER CONNECTOR, CHECK VOLTAGE BETWEEN TERMINAL AC2 OF A/C AMPLIFIER CONNECTOR AND BODY GROUND.
- Remove glove compartment.
- Disconnect A/C amplifier connector.
- Turn ignition switch ON.



- Measure voltage between terminal AC2 of A/C amplifier connector and body ground.

Voltage: 9.0 - 14.0 volts

- If OK proceed to step 4.
- If not OK check and replace A/C amplifier.

4. CHECK FOR OPEN AND SHORT IN HARNESS AND CONNECTOR BETWEEN ECM AND A/C AMPLIFIER.
- If OK check and replace ECM.
- If not OK repair or replace harness or connector.