Faulty Signal. Permanent Fault

Checking Instrument
- Check to see if the car has a VDO or Yazaki Combined Instrument Panel. The upper combined instrument panel is a VDO and the lower a Yazaki (see image).

If the Combined Instrument Panel is a VDO:
^ Proceed to Checking Diagnostic Trouble Codes In The Combined Instrument Panel section below.

If the Combined Instrument Panel is a Yazaki:
^ Proceed to test step below.





Checking The Speedometer
- Test drive the car.
- Check speedometer is operating correctly.

If reading is OK:
^ Proceed to Checking Vehicle Speed Signal section below.

If reading is Incorrect:
^ Proceed to test step below.





Checking Diagnostic Trouble Codes In The ABS System.
- Check to see if any DTCs are stored in the ABS system.
- Are any diagnostic trouble codes (DTCs) stored in the ABS system?

Yes:
^ Fault-trace any diagnostic trouble codes (DTCs) stored in the ABS system.
^ Then proceed to Verification section below.

No:
^ Proceed to test step below.





Checking Vehicle Speed Signal
- Connect the test box and check ground terminals.
- Connect engine control module (ECM).
- Gear lever in Neutral.
- Raise car so that front wheels hang free
- Ignition on.
- Connect a voltmeter between connectors # 18 (# B18) and # 28 (# B28) on the test box.
- Rotate the front wheels.

NOTE: When the rear wheels are stationary and the front wheels are rotated diagnostic trouble codes (DTCs) may can be stored in the ABS system. Erase diagnostic trouble codes (DTCs) in the ABS system after fault-tracing.

- The voltmeter reading should oscillate between approx. 0.5 Volts and above battery voltage.

If reading is OK:
^ The diagnostic trouble code was caused by loose connections in the engine control module connector. Check connector for contact resistance and oxidation.
^ Then proceed to Verification section below.

If reading is incorrect:
^ Proceed to test step below.





Checking Signal Cable Voltage
- Test box connected
- Gear lever in Neutral.
- Raise car so that front wheels hang free
- Ignition on.
- Connect a voltmeter between connectors # 18 (# B18) and # 28 (# B28) on the test box.
- Rotate the front wheels.

NOTE: When the rear wheels are stationary and the front wheels are rotated diagnostic trouble codes (DTCs) may can be stored in the ABS system. Erase any diagnostic trouble codes (DTCs) stored in the ABS system after fault-tracing.

- The voltmeter reading should oscillate between approx. 0.5 Volts and above battery voltage.

If reading is 0 V:
^ Check cable between the combined instrument panel terminal A7 and engine control module # B118 for a short-circuit to ground.

If reading is 5 V:
^ Proceed to test step below.





Checking signal cable
- Test box connected.
- Ignition on.
- Connect a test light between terminals # 18 # B118 and # 28 (# B28) on the test box.
- The test light should not light.

If reading is OK:
^ Check cable between the combined instrument panel terminal A7 and engine control module # B118 for an open-circuit.
^ Then proceed to Verification section below.

If reading is incorrect:
^ Check cable between the combined instrument panel terminal A7 and engine control module # B18 for a short-circuit to supply voltage.
^ Then proceed to Verification section below.





Checking Diagnostic Trouble Codes In The Combined Instrument Panel
- Ignition on.
- Read off diagnostic trouble codes.
- Are any diagnostic trouble codes stored?

Yes:
^ Fault-trace the combined instrument panel diagnostic trouble codes.
^ Then proceed to Verification section below.

No:
^ Proceed to test step below.





Checking Vehicle Speed Signal
- Connect the test box and check ground terminals.
- Connect engine control module.
- Gear lever in Neutral.
- Raise car so that front wheels hang free.
- Ignition on.
- Connect a voltmeter between connectors # 18 (# B18) and # 28 (# B28) on the test box.
- Rotate the front wheels.

NOTE: When the rear wheels are stationary and the front wheels are rotated diagnostic trouble codes (DTCs) may can be stored in the ABS system. Erase diagnostic trouble codes (DTCs) in the ABS system after fault-tracing.

- The voltmeter reading should oscillate between approx. 0.5 Volts and above battery voltage.

If reading is OK:
^ The diagnostic trouble code was caused by loose connections in the engine control module connector. Check connector for contact resistance and oxidation.
^ Then proceed to Verification section below.

If reading is incorrect:
^ Proceed to test step below.





Checking Signal Cable
- Ignition off.
- Test box connected.
- Expose the rear portion of the combined instrument panel.
- Connect an ohmmeter between combined instrument panel connector A terminal 7 and # 18 (# A1 8) on the test box.
- The ohmmeter should read approx. 0 ohms.

If reading is OK:
^ Fault-trace combined instrument panel and vehicle speed sensor (VSS) circuit.
^ Then proceed to Verification section below.

If reading is incorrect:
^ Check cable between the combined instrument panel terminal A7 and engine control module # B18 for an open-circuit.
^ Then proceed to Verification section below.





Verification
- After carrying out the repair, check that the fault has been remedied as follows.
- Ignition off.
- Control module connected.
- Combined instrument panel connected.
- Test drive the car.
- Go into scrolling value list.
- Read off the speedometer signal.
- Is the correct speedometer signal displayed?

Yes:
^ Fault corrected

No:
^ Proceed to test step below.

Fault-tracing Information
The verification result shows that the fault persists.

- Do you want to exit fault-tracing?

Yes:
^ Fault not corrected

No:
^ Return to Checking Instrument section above.