Potentiometer Signal Too Low

Diagnostic trouble code (DTC) information





Condition
Motor 2 controls the backrest angle. If the voltage from the potentiometer for motor 2 to control module terminal V2 falls below 0.2 V diagnostic trouble code (DTC) PSL/PSR-222 is set.

Possible source
- Contact resistance in terminals.
- Loose contacts in terminals.
- Faulty potentiometer. motor 2.
- Open-circuit in supply lead between control module and potentiometer, motor 2.
- Open-circuit in signal lead between control module and potentiometer, motor 2.
- Signal lead between control module and potentiometer to motor 2 short-circuited to ground.
- Defective control module.

Fault symptom(s)
- Memory activation does not work.
- Fault-tracing begins at FB. Potentiometer signal too low.





F B. Potentiometer signal too low

FB1: Checking status
- Ignition OFF.
Select scrolling values and read off the value from the potentiometer for motor 2.

Move the seat backrest forward and backward between the seat end positions several times using the control button.

The potentiometer value must not fall below 0.2 V at any time.

It reading is OK:
- FB14

If reading is incorrect:
- FB2








FB2: Checking resistance in circuit to potentiometer
- Ignition OFF.
- Remove seat from car.
- Disconnect gray 14-pin connector B.
Connect an ohmmeter between positions B:4 and B:5 on gray 14-pin connector (potentiometer side).

The ohmmeter should read approx. 2200 ohm.

If reading is OK:
- FB8

If reading is incorrect:
- FB3





FB3: Checking potentiometer resistance
- Ignition OFF.
- Disconnect the gray 14-pin connector.
- Remove potentiometer on motor 2.
Connect an ohmmeter between two outer terminals on the potentiometer.

The ohmmeter should read approx. 2200 ohm.

It reading is OK:
- FB5

If reading is incorrect:
- FB4





FB4: Replace component
Test with new potentiometer.
Then continue with:
- FB12

FB5: Checking supply leads to potentiometer
- Ignition OFF.
- Disconnect 3pin connector to potentiometer on motor 2.
- Disconnect the gray 14-pin connector B.
Connect an ohmmeter between the gray 14-pin connector terminal B:5 and the corresponding terminal on the 3-pin connector (blue/white lead).

The ohmmeter should read approx. 0 ohm.

If reading is OK:
- FB7

If reading is incorrect:
- FB6





FB6: Checking for an open-circuit
Check the blue/white supply lead between the control module, position B:5, and the potentiometer for open circuit.

Then continue with:
- FB12





FB7: Checking, contact resistance and oxidation
Check the 3-pin connector to the potentiometer on motor 2 for contact resistance and oxidation.

Then continue with:
- FB12





FB8: Checking potentiometer's signal lead
- Ignition OFF.
- Disconnect the gray 14-pin connector B.
Connect an ohmmeter between positions B:3 and B:5 on gray 14-pin connector (potentiometer side).

The ohmmeter should read between 100 - 2200 ohm depending on seat position.

If reading is OK:
- FB11

If value is lower:
- FB9

If value is higher:
- FB10





FB9: Checking for a short-circuit
Check the white signal lead between position B:3, and the potentiometer on motor 2 for short-circuit to ground.

Then continue with:
- FB12





FB10: Checking for an open-circuit
Check the white signal lead between position B:3, and the potentiometer on motor 2 for open-circuit to supply.

Then continue with:
- FB12





FB11: Checking control module and connector B
There are no faults on the potentiometer and leads.
Check and correct the 14-pin gray connector B for contact resistance and oxidation.

If diagnostic trouble code (DTC) persists after verification, try a new control module. Control module, Service and Repair

Then continue with:
- FB12





FB12: Verification
Hint: After carrying out the repair, check that the fault has been remedied as follows:
- Ignition OFF.
- Reinstall components, connectors etc.
- Connect up seat in car. Wiring up for voltage measurement, Wiring Up For Voltage Measurement

Select scrolling values and read off the value from the potentiometer for motor 2.

Operate the backrest forward/backward, running it to the stop positions in both directions.

The values indicated for potentiometer 2 must not be more than 4.6 V or less than 0.2 V.

If reading is OK:
- Fault corrected

If reading is incorrect:
- FB13

FB13: Fault-tracing information
The verification result shows that the fault persists.
Do you want to exit fault-tracing?

Yes:
- Fault not corrected

No:
- FB1








FB14: Intermittent fault
Check the gray 14-pin connector B on the control module and connector on the potentiometer on motor 2 for loose contacts and contact resistance and oxidation.

Check the blue/white supply lead between the control module position B:5, and the potentiometer on motor 2 for intermittent open-circuit.

Check the white signal lead between control module position B:3, and the potentiometer on motor 2 for intermittent short-circuit to ground.

If the the fault persists after all checks are completed the fault might be due to linearity fault in the potentiometer. Replace potentiometer on motor 2 with a new one.

Then continue with:
- FB15

FB15: 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:
- FB1

No:
- Operation done.