JH: Tachometer Output Failure
JH: Introduction See: JH: Tachometer Output Failure - Introduction
JH1 CHECK CTO CIRCUIT FOR SHORT TO POWER IN HARNESS
- Disconnect PCM.
- Key on, engine off.
- Measure voltage of CTO circuit between PCM harness connector pin 48 and ground.
Is the voltage less than 0.5 volt?
Yes
.
No
- REPAIR short circuit. VERIFY symptom no longer exists.
JH2 CHECK CTO CIRCUIT FOR SHORT TO GROUND IN HARNESS
- Disconnect instrument cluster connector.
- Measure resistance between PCM harness connector pin 48 and battery negative post.
- Measure resistance between PCM harness connector pin 48 and chassis ground.
Are both resistances greater than 10,000 ohms?
Yes
.
No
- REPAIR short circuit. VERIFY a symptom no longer exists.
JH3 CHECK CTO CIRCUIT FOR OPEN IN HARNESS
- Measure resistance between PCM harness connector pin 48 and instrument cluster harness pin.
Is the resistance less than 5.0 ohms?
Yes
.
No
- REPAIR open circuit. VERIFY symptom no longer exists.
JH4 CHECK CTO SIGNAL FROM PCM
- Reconnect PCM.
- Start engine.
- Measure voltage between CTO pin at the instrument cluster and battery negative post.
Is voltage between 3.0 and 9.0 volts?
Yes
- REFER to the Instrument Panel, Gauges and Warning Indicators.
No
|