DTC 233

EJ. DTC 2-3-3
2-3-3 VSS faulty

Principle of operation

The signal from the combined instrument to the TCM is a uniform square wave of variable frequency, the number of pulses (i.e. frequency) increasing with speed. The signal is used to verify that the transmission shifts at the correct speed.

Fault description

The signal from the combined instrument should consist of a continuous stream of pulses. If the signal is subjected to interference, pulses may be lost or additional pulses added, and DTC 2-3-3 will be recorded. The 'loss' of pulses may be due to poor contact at some point in the circuit, while additional pulses are usually created by interference from some adjoining system. The TCM emergency program is activated, the lock-up function is inoperable and gearshifting is 'hard'. The MIL on the combined instrument lights.





Circuit description

The circuit consists of the TCM, combined instrument, VSS and connectors.





1
Checking speedometer while driving

Check that speedometer reading is reasonable when car is driven. If not, fault is in combined instrument or VSS circuit.

Also check that fuel injection and ignition system is supplying correct information through test mode 1 in Motronic 1.8. How to display codes for Motronic 1.8 can be found in Computers and Control Systems, Testing and Inspection. Testing and Inspection

WARNING!
Exercise due care when performing troubleshooting with freely rotating rear wheels. Use jack stands if the back of the car is jacked for tests with freely rotating wheels. Keep the rear wheels clear of other persons.





2
Checking VSS to TCM

- Switch off ignition.
- Move gear selector to position N.
- Jack up car so that rear wheels are free to turn.
- Connect break-out box between TCM and wiring.
- Switch on ignition.

Connect voltmeter across # 38 (SPM) and # 12 (SG).

- Instrument should indicate close to battery voltage.

Block one rear wheel and rotate other wheel rapidly to spin propeller shaft.

- Instrument should indicate 4-7 V.

If signal is present, return to Testing and Inspection. Diagnostic Procedures

If fault is still present after test driving, replace TCM.

- If no signal is present, proceed to step 3.





3
Measure output signal from combined instrument

- Switch off ignition.
- Move gear selector to position N.
- Jack up car so that rear wheels are free to turn.
- Switch on ignition.

Connect voltmeter across terminal 3A (SPM) on combined instrument and # 12 (SG) on break-out box.

Block one rear wheel and rotate other wheel rapidly to spin propeller shaft. Instrument should indicate 4-7 V.

- If no signal is present and results of step 1 are correct, output on combined instrument is faulty.

If signal is OK, proceed to step 4.





4
Measuring resistance of VSS lead

- Switch off ignition.

Connect ohmmeter between # 38 (SPM) and terminal 3A on combined instrument.

- Instrument should indicate approx. 0 Ohm if lead not open-circuited.

If readings are correct, check that no leads (e.g. ignition leads, car phone etc.) are run or other systems (radio etc.) installed so as to cause interference.

Return to Testing and Inspection. Diagnostic Procedures

- If instrument indicates different value, proceed to next step.





5
Checking ground terminals (signal ground and power ground) on TCM

- Switch on ignition.
- Leave break-out box connected between AW3O-40/AW3O-43 TCM and wiring.

Connect voltmeter across # 11 (PG) and # 12 (SG).

- Instrument should indicate less than 0.7 volt, otherwise ground connections are poor. In this case, check leads and connections to ground terminals as described in Testing and Inspection. Component Tests and General Diagnostics

Return to Testing and Inspection. Diagnostic Procedures

- If reading is OK, proceed to next step.


6
Check speedometer ground connection