Tachometer Inoperative

Use this fault-tracing procedure if other instrument panel gauges are working.

Sources of Fault:





- Signal lead short-circuited to battery supply.
- Signal lead short-circuited to ground.
- Open-circuit in signal lead.
- Excess contact resistance.
- Fault in engine management system.

Start fault-tracing at step 1, below.

1) Checking Signal Lead to Instrument Panel:





- Ignition off.
- Expose instrument panel. (Remove Dash Board Cover) Service and Repair
- Undo instrument panel connector.
- Connect test box to cable harness connector and check ground points. Connecting Test Box





- Connect test box between instrument panel and cable harness connectors.
- Start engine.





- Connect a voltmeter across # 11 (# A11) and # 15 (# A15) on test box.
- Voltmeter should read approx. 6.5 V.

If reading is correct: (approx. 6.5 V)
- Intermittent open-circuit in signal lead between instrument panel terminal # A11 and engine management system terminal # B21 or ignition control module terminal # B29, depending on type of engine management system.
# B21: Fenix 5.2, Motronic 4.3
# B29: LH 3.2, EZ-K.
- Check signal lead and connections for loose contact and contact resistance. Checking Cables and Terminals
- If tachometer still does not work after checking signal lead, replace tachometer. Service and Repair (Individual Component Replacement)

If voltmeter reads 0 V:
- Open-circuit or short-circuit to ground in signal lead between instrument panel terminal # A11 and engine management system terminal # B21 or ignition control module terminal # B29, depending on type of engine management system.
# B21: Fenix 5.2, Motronic 4.3
# B29: LH 3.2, EZ-K.
- Check signal lead and connection for open-circuit and short-circuit to ground. Checking Cables and Terminals

If voltmeter reading equals battery voltage:
- Short-circuit to battery supply in signal lead between instrument panel terminal # A11 and engine management system terminal # B21 or ignition control module # B29, depending on engine management system.
# B21: Fenix 5.2, Motronic 4.3
# B29: LH 3.2, EZ-K.
- Check signal lead and connection for short-circuit to battery supply. Checking Cables and Terminals