DTC 143

DP. DTC 1-4-3
1-4-3 Short-circuit to ground in kickdown switch circuit

Principle of operation

The kickdown switch is mounted beside the throttle cable opening in the firewall. The switch is closed by pressure from the cable sleeve when the accelerator pedal (AP) is pressed to the floor. The signal from the switch is supplied to the TCM, in which it is used in computing downshifting required by sudden acceleration.

Fault description

The kickdown switch is stuck or the circuit between the switch and TCM is shorted to ground.
Troubleshooting should indicate if the fault is in the wiring, if the switch is stuck or if it is faulty, also whether the throttle signal is incorrect or the fault is in the TCM. If the throttle signal is low (less than 87% at WOT), the fault will occur on kickdown.





Circuit description

The circuit consists of the TCM, associated wiring and kickdown switch.





1
Testing kickdown switch In test mode 2

Test kickdown switch in test mode 2 Displaying & Reading Trouble Codes






- If response code is correct, fault is occurring only intermittently under particular conditions, making it considerably more difficult to locate.

Proceed to following step.





2
Measuring resistance of kickdown switch and leads

- Switch off ignition.
- Connect break-out box to wiring.

Connect ohmmeter between # 25 (KD) and # 12 (SG).

- If instrument indicates approx. 0 Ohm with AP pressed to floor and infinity in all other positions, kick- down switch and leads are OK.
In this case, fault is due to intermittent fault. Return to Testing and Inspection. Diagnostic Procedures

- If instrument indicates other value, proceed to following step.





3
Measuring resistance of kickdown switch

- Switch off ignition.

Connect ohmmeter between terminals on base of switch.

- If instrument indicates approx. 0 Ohm with AP pressed to floor and infinity in all other positions, kickdown switch and leads are OK.
Check leads for short-circuit to ground. Also check ground terminal connection.
Return to Testing and Inspection. Diagnostic Procedures

- If instrument indicates other value, switch is faulty. In this case, replace switch.





4
Measuring TP sensor signal In test mode 5

Measure TP sensor signal as function of AP position. Displaying & Reading Trouble Codes

Check difference between WOT and kickdown positions.

- TP sensor signal is faulty if too low (less than 87% of WOT opening in kickdown position) Carry out troubleshooting as per DTC 2-2-3 'TP sensor signal too low'.