Signal Too Low

NOTE: To get the correct status message carry out the following before reading the diagnostic trouble code (DTC).





Status Message
- Ignition ON.
- Accelerator pedal (AP) up.
- Wait for about 10 seconds.
- Push down the accelerator pedal completely, keep it fully depressed in kickdown mode.
- Wait for about 10 seconds.
- Read off diagnostic trouble code.
- Does the status indicate PERMANENT FAULT?

Yes:
- Proceed to: Checking Kickdown Switch Function section below.

No:
- Proceed to: Intermittent Fault section below.





Checking Kickdown Switch Function
- Ignition ON.
- Go into scrolling values.
- Read off kickdown switch position.
- The reading should only be ON if the accelerator pedal is depressed to kickdown position. In other accelerator pedal positions the reading should be OFF.
- Is the correct reading displayed?

Yes:
- Proceed to: Checking Voltage Drop Over The Engine Control Module Signal Ground. section below.

No:
- Proceed to: Checking The Kickdown Switch section below.





Checking The Kickdown Switch
- When the accelerator pedal AP is depressed fully a circuit is made when the sheath on the throttle cable is pressed into the kickdown switch. Releasing the accelerator pedal allows the cable sheath to spring back and the switch breaks the circuit.

NOTE: The kickdown switch is operated only when the accelerator pedal is fully depressed.

- Check that the cable sheath is pressed in and springs back when the accelerator pedal is operated.
- Are kickdown switch and cable operation OK?

Yes:
- Proceed to: Checking Kickdown Switch Resistance section below.

No:
- Proceed to: Fault-tracing Information section below.

Fault-tracing Information
- Repair as necessary.
- Proceed to: Verification section below.





Checking Kickdown Switch Resistance
- Ignition OFF.
- Disconnect the kickdown switch.
- Connect an ohmmeter between kickdown switch terminals 1 and 2.
- Fully depress the accelerator pedal.
- The ohmmeter should read approx 0 Ohms with the accelerator pedal fully depressed and infinite resistance in all other positions.
- Is the correct reading displayed?

Yes:
- Proceed to: Checking For A Short-circuit section below.

No:
- Proceed to: Replacing Component section below.





Checking For A Short-circuit
- Check cable between kickdown switch terminal 1 and transmission control module (TCM) # 18 for a short-circuit to ground.
- Proceed to: Verification section below.





Replacing Component
- Ignition OFF.
- Try a new kickdown switch.
- Proceed to: Verification section below.





Checking Voltage Drop Over The Engine Control Module Signal Ground.
- Ignition OFF.
- Connect a test box to engine control module (ECM).
- Engine control module connected.
- Ignition ON.
- Turn on as many power consuming items as possible.
- Connect a voltmeter between # 42 (# A42) on the test box and ground terminal 31/33.
- Note the voltmeter reading.
- Proceed to: Connecting The Test Box section below.





Connecting The Test Box
- Ignition OFF.
- Disconnect the test box from the engine control module.
- Connect a test box to the automatic transmission control module and check ground terminals.
- Proceed to: Checking Voltage Drop Over The Transmission Control Module Signal Ground section below.





Checking Voltage Drop Over The Transmission Control Module Signal Ground
- Ignition OFF.
- Connect the control modules.
- Ignition ON.
- Turn on as many power consuming items as possible.
- Connect a voltmeter between # 15 on the test box and ground terminal 31/53. Note the reading. Add the previous reading to the new reading.
- When added together the sum of the two readings should not be more than 0.1 Volts.

If reading is OK:
- Proceed to: Adaptation Of The Throttle Position Sensor Signal section below.

If reading is incorrect:
- Proceed to: Checking For Contact Resistance And Oxidation section below.





Checking For Contact Resistance And Oxidation
- Ignition OFF.
- Check ground terminal 31/53 and transmission control module connectors for contact resistance and oxidation.
- Proceed to: Verification section below.





Adaptation Of The Throttle Position Sensor Signal
- If the control module has been replaced the throttle position (TP) signal must be adapted to match the new module. Failure to adapt the signal can result in diagnostic trouble code AT-143 being stored. Carry out adaptation to wide open throttle WOT as follows:

- Block all four wheels.
- Start the engine.

CAUTION: Apply parking brake and press down hard on the brake pedal with left foot throughout the procedure.

- Gear selector to position D.
- Fully depress the accelerator pedal so the kick- down switch closes.
- Keep accelerator pedal fully depressed for 5 seconds.
- Release the accelerator pedal and move gear selector to position P.

- Wide open throttle (WOT) is now adapted.
- Proceed to: Checking Throttle Position Sensor Signal section below.





Checking Throttle Position Sensor Signal
- Ignition OFF.
- Go into scrolling values.
- Read off throttle position sensor and kickdown switch positions.
- Depress the accelerator pedal to just before kick- down position. Check that the throttle position sensor position reads wide open throttle.

NOTE: The kickdown switch should not be moved during the test, it should read OFF.

- Is the throttle position sensor position more than 95% wide open throttle?

Yes:
- Proceed to Fault-tracing Information section below.

No:
- Proceed to Fault-tracing Information 2 sections below.

Fault-tracing Information
- The diagnostic trouble code was caused by incorrect adaptation of the throttle position sensor signal.
- Proceed to Fault-tracing Information section below.

Fault-tracing Information
- Fault-trace throttle position sensor signal diagnostic trouble code AT-223. AT-223 Throttle Position Sensor
- Proceed to: Verification section below.





Verification
- After repairs have been completed they must be verified as follows to ensure that the fault has been eliminated:

- Ignition OFF.
- Reconnect the connectors, reinstall components etc.
- Ignition ON.
- Brake pedal up.
- Wait approx. 10 seconds.
- Push down the accelerator pedal completely, keep it fully depressed in kickdown mode.
- Wait approx. 10 seconds.

- Read off the diagnostic trouble code status.
- Does the status display INTERMITTENT FAULT?

Yes:
- Fault corrected.

No:
- Proceed to: Fault-tracing Information section below.

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

- Do you want to exit fault-tracing?

Yes:
- Fault not corrected.

No:
- Proceed to: Status Message section above.





Intermittent Fault
- Check that the kickdown switch and cable sheath are operating correctly and are not sticking or stiff.
- Check the cable between kickdown switch terminal 1 and control module # 18 for an intermittent short-circuit to ground.
- Check throttle position sensor signal for an intermittent fault.
- Proceed to: Fault-tracing Information section below.

Fault-tracing Information
For intermittent faults fault-tracing is not followed by a verification because the fault is not present at this moment.

- Do you want to repeat fault-tracing?

Yes:
- Proceed to: Status Message section above.

No:
- Operation done.