There is no tach - rpm sensor . This information comes from the PCM - engine computer .
Tachometer
The tachometer is a 6,000 rpm tachometer. It has four terminals labeled "B" (12 to 14.5V), "S" (EDIS tach signal in), and two "G" (cylinder selection grounds). The top ground (G) terminal is open on a 4-cylinder engine vehicle, and is grounded on a 6-cylinder engine vehicle.
- The tachometer is inoperative
- Powertrain control module (PCM).
- Circuitry.
- Tachometer.
- Instrument cluster printed circuit.
- Incorrect tachometer indication
- Circuitry.
- Instrument cluster printed circuit.
- Tachometer.
Measure the resistance between the instrument cluster C220c pin 8, circuit 398 (BK/YE), harness side and ground.
- Is the resistance less than 5 ohms?
Yes GO to G2 .
No REPAIR the circuit. TEST the system for normal operation.
Measure the resistance between the tachometer and the instrument cluster printed circuit terminals; refer to the following chart:
Instrument Cluster Printed Circuit Terminal
Tachometer Terminal
C220a pin 13
C220a pin 15
S
C220b pin 2
G
C220c pin 8
G (6 CYL.)
- Are the resistances less than 5 ohms?
Yes GO to G3 .
No INSTALL a new instrument cluster printed circuit. REFER to Instrument Cluster Printed Circuit in this section. TEST the system for normal operation.
G3 CHECK FOR CLEAN TACH OUT (CTO) CIRCUIT OPEN OR SHORT
Check for CTO circuit open or short. Refer to Powertrain Control/Emissions Diagnosis (PC/ED) manual.
Yes INSTALL a new tachometer. REFER to Gauges in this section. TEST the system for normal operation.
No GO to G4 .
G4 CHECK FOR CORRECT PCM OPERATION
Disconnect all PCM connectors.
Check for:
- corrosion
- pushed-out pins
Connect all PCM connectors and make sure they seat correctly.
Operate the system and verify the concern is still present.
- Is the concern still present?
Yes INSTALL a new PCM. REFER to Section 303-14 . CLEAR the DTCs. REPEAT the PCM self-test.
No The system is operating correctly at this time. Concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.
Your best bet mite be to take it to a qualified repair shop.
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