DTC 143

EAP Code 1-4-3

1-4-3 Short-circuit to ground in kickdown switch circuit

DTC information

Conditions for DTC






The signal from the kick-down switch is sent to the control module where it affects functions, such as downshifting during rapid accelerations. The kick-down switch closes when the outer sleeve on the accelerator cable is pressed against the switch, i.e., fully depressed AP. If the TCM registers that the kick-down switch circuit is short-circuited to ground when the throttle opening is less than approx. 85%, the DTC 1-4-3 is set.

NOTE: If the throttle position sensor (TP) provides a signal that is too low, that is to say less than 85% with WOT (Wide Open Throttle), then the kick-down switch will be affected and DTC 1-4-3 is set.


Substitution value

No substitution value

Defect cause

- Short circuit to ground in the signal wiring.
- Kickdown switch malfunction
- Incorrect signal from throttle position sensor TP
- New TCM installed but no adaptation of throttle position sensor signal has been carried out.


Fault symptom

- No fault symptom.
- Fault-tracing starts with EAP1



EAP1

Checking the kick-down switch operation






- Ignition ON.
- Set gearshift selector to position P.

Check kick-down switch operation using Diagnostic Test Mode 2. Diagnostic Test Mode 2

NOTE: The response code is given only when the accelerator pedal AP is fully depressed to the kick- down position.






If the kick-down switch is OK:
- Adaptation of the throttle position TP signal EAP5.

If the kick-down switch is not operating:
-^ Checking voltage drop over signal ground EAP2.



EAP2

Checking voltage drop over signal ground






- Ignition OFF
- Connect test box and check ground points as per GB1-GB2 GB. Connecting the Test Box

- Connect a test box to the engine control module (ECM MFI Fenix 5.2, LH 3.2, or Motronic 4.3).
- Connect the control modules
- Ignition ON.
- Turn on as many power consuming items as possible.

Connect a voltmeter between the transmission test box #20 (#A20) and the ECM module test box:






- Fenix 5,2 MFI control module: #42 (#A42) (signal ground, control module)
- LH 3,2 MFI control module: #20 (#A20) (signal ground, control module)
- Motronic 4,3 MFI control module: #42 (#A42) (signal ground, control module)

The voltmeter should read less than 0.10 V.







If reading is OK:
- Checking the kickdown switch EAP3.

If reading is incorrect:
- Check ground point 31/33, wiring between the ground point and the TCM and ECM modules for contact resistance and oxidation as per FA6. FA. Checking Wiring and Connections

Then continue with: Checking the kick-down switch EAP3.



EAP3

Checking the kick-down switch






When the accelerator pedal AP is depressed fully a circuit is made when the sheath on the throttle cable is pressed in to the kick-down switch. Releasing the AP allows the cable sheath to spring back and the switch breaks the circuit.


NOTE: The kick-down switch is operated only when the AP is pressed fully down.


Check that the cable sheath is pressed in and springs back when the AP is operated.

If the kickdown switch and cable are OK:
- Checking kick-down switch resistance EAP4.

If the kick-down switch or cable operation is not OK:
- Correct faults as required.



EAP4

Checking kick-down switch resistance






- Ignition OFF
- Disconnect the kick-down switch.

Connect an ohmmeter between terminals 1 and 2 on the kick-down switch.
Fully depress the accelerator pedal AP.

The ohmmeter should read approx 0 Ohms with AP fully depressed and infinity in all other positions.

If the readings are OK:
- Check the cable between the kick-down switch terminal 2 and the TCM #B30 for short circuit to ground as per FA3. FA. Checking Wiring and Connections

If any reading is incorrect:
- Try a new kick-down switch as per Q1-Q8.



EAP5

Adaptation of the throttle position (TP) signal






If a new TCM has been installed the throttle position TP signal must be adapted to match the new module. Failure to adapt the TCM to the TP signal can result in DTC 1-4-3 being set.

To carry out adaptation to wide open throttle WOT proceed as follows:

- Block all four wheels
- Start engine.

Important! Apply parking brake and press down hard on the brake pedal with left foot during the entire procedure.






- Set gearsh itt selector to position D
- Fully depress the accelerator pedal (AP) so the kick-down switch closes.
- Keep the AP fully depressed for 5 seconds
- Release the AP and set the gearshift selector to position P

WOT is now adapted to the new TCM.

Then continue with: Checking the TP signal EAP6.



EAP6

Checking the throttle position TP signal






- Ignition ON.
- Set gearsh itt selector to position P

Using Diagnostic Test Mode 5 check that when the AP is depressed to a position exactly prior to kick-down activation, the TP signal is at WOT (wide open throttle).

NOTE: The Kick-down should not be activated during the check.






If reading is OK:
- Intermittent fault. Fault-tracing as per EAP7.

If the value is less than approx. 95% at WOT:
- Fault-tracing TP signal as per EAV. Diagnostic Trouble Code 2-2-3 Throttle position (TP) signal too low. DTC 223



EAP7

Intermittent Fault.

Checking wiring and connections






- Check that the kick-down switch or cable sheath are operating correctly and are not sticking or stiff.

- Check the wiring between the kick-down switch terminal 2 and the TCM #B30 for intermittent short circuit to ground as per FA3. FA. Checking Wiring and Connections

- Check the TP signal as per EAV. DTC 2-2-3 Throttle position signal too low, for intermittent fault. DTC 223