Signal Missing - Permanent Fault

ECM-2A0A REAR HEATED OXYGEN SENSOR (HO2S)
SIGNAL MISSING - PERMANENT FAULT

Checking Connector




CAUTION!
Do not apply rust solvent spray or grease to the Heated Oxygen Sensor (HO2S) connector.

- Ignition off.
- Check Heated Oxygen Sensor (HO2S) connector for contact resistance and oxidation according to [1][2]Checking Wiring and Terminals. Permanent Fault
- reconnect connectors etc.
- Start the engine and let it idle.

Read the signal for the rear Heated Oxygen Sensor (HO2S).

NOTE: It may take up to approximately 3 minutes before fuel trim has begun and the signal can be Read.

Check that the signal is within its permitted range. The signal should be free of disturbances and above 0.6 V or below 0.3 V.

If signal is now OK this indicates that the fault was caused by poor contact in the connector.

Other information
- To access/replace the heated oxygen sensor (HO2S), Adapter Wiring Switch, Replacing
- For information about signals, see Diagnostic Parameters and Pinout Values. Signal Description, ME7, B5XX4T

Is the signal OK?
Yes - Testing Complete.
No - Contine below.


Checking wiring and components



Check the signal cable (+) between Heated Oxygen Sensor (HO2S) # 4 and control module # A61 (# B1) and the signal cable (-) between Heated Oxygen Sensor (HO2S) # 3 and control module # A62 (# B2) for an open-circuit according to [1][2]Checking Wiring and Terminals. Permanent Fault

If wiring is OK, try another Heated Oxygen Sensor (HO2S).

Remedy as necessary.

Other information
- Connecting the breakout box/accessing the control module Connecting the Breakout Box (ECM)
- To access/replace the heated oxygen sensor (HO2S), Adapter Wiring Switch, Replacing
- For information about signals, see Diagnostic Parameters and Pinout Values. Signal Description, ME7, B5XX4T


Verification



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

- Ignition off.
- Reconnect connectors, reinstall components
- Test drive car as follows:

A/C on Drive the car so that idle, normal and high speeds are reached. Let the car operate in these phases for a few minutes. Accelerate at full throttle a number of times so that high boost pressure is reached (applies only to turbo models). Total test drive time must be 15 minutes.

NOTE: After test driving the engine should not be turned off. The test drive must be carried out again.

Connect VIDA again and read out the Heated Oxygen Sensor (HO2S) Diagnostic Trouble Code (DTC) status.
The text NOT READY is displayed if diagnosis is underway.

Is FAULT NOT REGISTERED displayed?
Yes - Testing Complete.
No - Continue below.


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.