Tachometer Output Error. Isuzu Isuzu T-Series (Truck Line C) 2002

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 2002 🢒 Isuzu T-Series (Truck Line C) 🢒 Engine 🢒 Engine Electrical 🢒 Tachometer Output Error

When the crankshaft position (CKP) sensor and CAM sensor are erratic tachometer output could become abnormal. If vehicle running performance is adversely affected, repair the abnormality first.

Unless the CKP sensor and CAM sensor signal are both normal, tachometer has no output.

•	The engine control module (ECM) delivers shortwave of 17.5 pulse (0-5 volts) per engine rotation to tachometer.

•	The tachometer does not produce an output at 230 RPM or less.

•	If inspecting by voltage, the DMM reads around 2.5 volts during engine idle, and 5 volts or 0 volts for abnormal output .

Step

Action

Value

Yes

Important: When the CKP sensor and the CAM sensor are unstable, the tachometer output becomes abnormal.

While the engine is running

•	When CKP sensor fails, a DTC sets.

•	When CAM sensor fails, a DTC sets.

After turning the ignition OFF, if either CKP sensor or CAM sensor is damaged, the malfunction indicator lamp (MIL) illuminates.
If the vehicles running performance is adversely affected, repair the performance fault first.
The tachometer output is not produced if a CKP or CMP sensor fault exists.

Does tachometer output error appear without CKP sensor error and CAM sensor error during engine in operation?

Go to Step 2

System OK

Important:

•	The ECM delivers a signal of 17.5 pulse (0-5 V) per engine rotation to tachometer.

•	The tachometer does not produce output at 230 RPM or less.

•	If checking by voltage, the DMM reads around 2.5 V under engine idling, and 5 V or 0 V for output abnormality.

Measure signal between pin number 69 (TACHO) and pin number 102 (ECM-GND) at ECM side.

Does the frequency measure near the specified value?

184 Hz

Go to Step 4

Go to Step 3

Disconnect the tachometer.
Measure the waveform .

Does the frequency measure near the specified value?

184 Hz

System OK

Go to Step 5

Replace the tachometer and/or repair the tachometer wiring harness.

Did you complete the action?

System OK

Replace the ECM, refer to Engine Control Module Replacement/Restore Fuel Rate Data .

Did you complete the replacement?

System OK