Part 2

Signal too low (Continued)

Checking ground terminals

- Ignition off.
- Control module disconnected.
- Turn of all equipment in the car that takes power from the battery (the interior lighting and radio etc).
Connect an ohmmeter between the battery negative terminal and:
#20 (#A20) on the breakout box
#29 (#A29) on the breakout box.

The ohmmeter should read approximately 0 ohms for all readings

OK - No Fault Found

Not OK - Checking for an open-circuit, contact resistance and oxidation

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Checking for an open-circuit, contact resistance and oxidation
Check ground terminals 31/32 and 31/33 and cables between ground terminals and control module #A20 and #A29 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault , and contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check ground lead between battery and bodywork for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault , and contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.

Select "Continue" when the fault has been repaired.

Continue - Verification

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Verification

Verification

Hint: After carrying out the repair check that the fault has been remedied.
Carry out the following:

- Ignition off
- Turn of all equipment in the car that takes power from the battery (the interior lighting and radio etc).
- Control module disconnected.
Connect an ohmmeter between the battery negative terminal and:
#20 (#A20) on the breakout box
#29 (#A29) on the breakout box.

The ohmmeter should read approximately 0 ohms for all readings

OK - VERIFIED

Not OK - VERIFICATION FAILED

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VERIFIED - FAULT FOUND

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information
Information
Attempt New Test - Checking ground terminals

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CONNECTED - Checking voltage drop over the transmission control module (TCM) signal ground

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Checking voltage drop over the transmission control module (TCM) signal ground

- Ignition off.
- Connect the control modules.
- Ignition on.
- Turn on as many power consuming components as possible.
Connect a voltmeter between ground terminal 31/33 and #20 (#A20) on the breakout box. Make a note of 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 V.

OK - Adaptation of the throttle position (TP) sensor signal

Not OK - Checking for contact resistance and oxidation

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Checking for contact resistance and oxidation

- Ignition off.
Check ground terminal 31/33 and transmission control module (TCM) connectors for contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.

Select "Continue" when the fault has been repaired.

Continue - Verification

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Adaptation of the throttle position (TP) sensor signal

Hint: 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 (DTC) AT-143 being stored.
Carry out adaptation of wide open throttle (WOT) position as follows:

- Block all four wheels.
- Start engine.

Caution! Apply parking brake and press down hard on the brake pedal with left foot throughout this procedure.

- Gear selector to position D.
- Fully depress the accelerator pedal (AP) so that the kickdown switch (KD) closes.
- Keep the accelerator pedal (AP) floored for 5 seconds .
- Release the accelerator pedal (AP) and move gear selector to position P.
Wide open throttle (WOT) position is now adapted.

Continue - Checking throttle position (TP) sensor signal

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Checking throttle position (TP) sensor signal

- Ignition off.
- Go into scrolling values.
- Read off throttle position (TP) sensor and kickdown switch positions.
Depress the accelerator pedal (AP) to just before kickdown position. Check that the throttle position (TP) sensor position reads wide open throttle (WOT).

Note! The kickdown switch (KD) should not be closed during the test, it should read OFF.

Is the throttle position (TP) sensor position more than 95% at wide open throttle (WOT)?

Yes - Verification

No - Signal Too Low - Status message

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Verification

Verification

Hint: 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 (AP) completely, keep it fully depressed in kickdown mode.
- Wait approx. 10 seconds.
Read off the diagnostic trouble code (DTC) status.

Does the status display INTERMITTENT FAULT?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFIED - FAULT FOUND

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information

Information

Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.

Do you want to exit fault-tracing?

Yes - Exit fault-tracing

No - Attempt New Test

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Attempt New Test - Status message

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Intermittent fault

Signal too low

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 2 and control module #B30 for an intermittent short-circuit to ground according to Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults.
- Check throttle position (TP) sensor signal according to Signal too low Signal Too Low for an intermittent fault.

Select "Continue" when the fault has been repaired.

Continue - Fault-tracing information

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Fault-tracing information

Information

Fault-tracing information
If the fault is intermittent, do not verify fault-tracing if the fault does not recur.
It is possible to view the information again, or leave fault-tracing for this diagnostic trouble code (DTC).

Do you want to view the information again?

Yes - Attempt New Test

No - FAULT FOUND

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Attempt New Test - Status message

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Signal too low

Status message

Note! To obtain the correct status message the ignition must be switched on for approx. 15 seconds before the diagnostic trouble code (DTC) is read off.

Read off diagnostic trouble code (DTC).

Is the status PERMANENT FAULT displayed?

Yes - Checking the throttle position (TP) sensor signal

No - Intermittent fault

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Other diagnostic trouble codes (DTCs)
Read off OTHER DTCs in engine management system (Fenix 5.2, LH 3.2, Motronic 4.3 or Motronic 4.4).

Are diagnostic trouble codes (DTCs) EFI-243 for the Fenix 5.2, EFI-411 for the LH 3.2, EFI-411 for the Motronic 4.3 or EFI-411 for the Motronic 4.4 stored?

Yes - Fault-tracing information

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Fault-tracing information
Fault-trace according to engine management system diagnostic trouble code (DTC) (EFI-243 for the Fenix 5.2, EFI-411 for the LH 3.2, EFI-411 for the Motronic 4.3 or EFI-411 for the Motronic 4.4).

Continue - Verification
FAULT-TRACING FAILED

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Checking the throttle position (TP) sensor signal

- Ignition on.
- Go into scrolling values.
- Read off the throttle position (TP) sensor signal.
Floor the accelerator pedal (AP) and check if the throttle position (TP) sensor signal increases.

Does the value increase?

Yes - Checking throttle position (TP) sensor circuit

No - Checking throttle position (TP) sensor circuit

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Checking signal cable resistance to ground

- Ignition off.
- Engine control module (ECM) disconnected (both control modules LH 3.2 and EZ129K).
- Disconnect the transmission control module (TCM).
Connect an ohmmeter between ground and the breakout box:
- #50 (#B20) for LH 3.2
- #20 (#B20) for Fenix 5.2, Motronic 4.3 and Motronic 4.4.

The ohmmeter should read approx. 0 ohms.

OK - Checking signal from engine control module (ECM)

Not OK - Checking for a short-circuit

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Checking for a short-circuit
- Check cable between transmission control module (TCM) #B20 and engine control module (ECM) #B20 (Fenix 5.2, LH 3.2, Motronic 4.3 or Motronic 4.4) for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
- On cars with engine control module (ECM) type LH 3.2/EZ129K, also check the cable between engine control module (ECM) LH 3.2 #B20 and EZ129 K #B20 for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault

Select "Continue" when the fault has been repaired.

Continue - Verification

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Checking signal from engine control module (ECM)

- Ignition off.
- Connect the engine control module (ECM).
- Ignition on.
Connect an voltmeter between ground and the breakout box:
- #50 (#B20) for LH 3.2
- #20 (#B20) for Fenix 5.2, Motronic 4.3 and Motronic 4.4.
The voltmeter should normally read approx 0.5 V at closed throttle position (CTP). The voltage should not drop below 0.1 V at closed throttle position (CTP).

Is the reading OK?

Yes - Connecting the breakout box

No - Checking throttle position (TP) sensor circuit

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Checking throttle position (TP) sensor circuit
Further fault-tracing depends on the vehicle's engine control module (ECM).

Select control module.

Fenix 5.2 - Signal faulty. Permanent fault - 2-4-3 TP sensor signal

LH 3.2 - Signal too low. Permanent fault - Checking supply lead

Motronic 4.3 - Signal too low. Permanent fault - 4-1-1 TP sensor signal

Motronic 4.4 - Signal too low. Permanent fault - EFI-411 Throttle position (TP) sensor signal

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Checking signal to the transmission control module (TCM)

- Ignition off.
- Engine control module (ECM) connected.
- Ignition on.
Connect a voltmeter between #50 (#B20) and #20 (#A20) on the breakout box.
The voltmeter should normally read approx 0.5 V at closed throttle position (CTP). The voltage should not drop below 0.1 V at closed throttle position (CTP).

Is the reading OK?

Yes - Checking for contact resistance and oxidation

No - Checking for an open-circuit

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Checking for contact resistance and oxidation

- Ignition off.
The cause of the diagnostic trouble code (DTC) has been loose connections in the control module connectors. Check control module connectors for contact resistance and oxidation and remedy according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.

Select "Continue" when the fault has been repaired.

Continue - Verification

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Checking for an open-circuit
Check cable between automatic transmission control module (TCM) #B20 and engine control module (ECM) #B20 for the Fenix 5.2, LH 3.2, Motronic 4.3 or Motronic 4.4 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.

Select "Continue" when the fault has been repaired.

Continue - Verification

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Checking voltage drop over the engine control module (ECM) signal ground.

- Ignition off.
- Engine control module (ECM) connected.
- Ignition on.
- Turn on as many power consuming components as possible.
Connect a voltmeter between ground terminals 31/33 and the breakout box:

Make a note of the voltmeter reading.

Continue - Connecting the breakout box

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Checking voltage drop over the transmission control module (TCM) signal ground

When added together the sum of the two readings should not be more than 0.1 V.

OK - Checking voltage drop over signal ground and power ground

Not OK - Checking for contact resistance and oxidation

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Checking for contact resistance and oxidation

- Ignition on.
- Turn on as many power consuming components as possible.
Connect a voltmeter between #20 (#A20) and #29 (#A29) on the breakout box.

The voltmeter should read less than 0.6 V.

OK - Checking throttle position (TP) sensor signal from engine control module (ECM)

Not OK - Checking for contact resistance and oxidation

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Checking for contact resistance and oxidation

- Ignition off.
Check ground terminals 31/32 and 31/33, the cables between the ground terminals and control module #A20 and #A29, and the control module connector for contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.

Select "Continue" when the fault has been repaired.

Continue - Verification

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Checking throttle position (TP) sensor signal from engine control module (ECM)

- Ignition on.
Connect a voltmeter between #50 (#B20) and #20 (#A20) on the breakout box.
The voltmeter should normally read approx 0.5 V at closed throttle position (CTP). The voltage should not drop below 0.1 V at closed throttle position (CTP).

Is the reading OK?

Yes - Checking for contact resistance and oxidation

No - Checking throttle position (TP) sensor circuit

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Checking for contact resistance and oxidation