Signal Too Low

ECM-2120 FRONT HEATED OXYGEN SENSOR (HO2S), CONTROL ELEMENT
SIGNAL TOO LOW

DTC status ECM-2120, front Heated Oxygen Sensor (HO2S), control



Note! When Reading the DTC status, other stored Diagnostic Trouble Codes (DTCs) and their status will be listed.

Read the DTC status. Check the status of the relevant Diagnostic Trouble Code (DTC).

Was the status of the relevant Diagnostic Trouble Code (DTC) displayed as permanent?
Yes - Skip to "Checking Connector"
No - Continue below.


Checking cables



Check front Heated Oxygen Sensor (HO2S) connector for contact resistance and oxidation according to [1][2]Checking Wiring and Terminals. Intermittent Faults

Check signal cable (+) between control module # A42 and Heated Oxygen Sensor (HO2S) connector terminal 4 for an intermittent open-circuit according to [1][2]Checking Wiring and Terminals. Intermittent Faults

Check signal cable (-) between control module # A41 and Heated Oxygen Sensor (HO2S) connector terminal 3 for an intermittent open-circuit according to [1][2]Checking Wiring and Terminals. Intermittent Faults

Other information
- To connect the breakout box, Connecting the Breakout Box (ECM)
- To access/replace the control module, Engine Control Module (ECM), Replacing
- To access/replace the heated oxygen sensor (HO2S), Heated Oxygen Sensor (HO2S), Replacing
- For information about signals, Pinout Values and Diagnostic Parameters


Fault-tracing information
If the fault is intermittent, do not verify fault-tracing if the fault does not recur.
--Testing Complete--


Checking connector



- Ignition off.

Check front Heated Oxygen Sensor (HO2S) connector for contact resistance and oxidation according to [1][2]Checking Wiring and Terminals. Permanent Fault

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

Remedy as necessary.

Other information:
- To access/replace the heated oxygen sensor (HO2S), Heated Oxygen Sensor (HO2S), Replacing
- For information about signals, Pinout Values and Diagnostic Parameters


Checking connector



- Ignition off.
- Reinstall components, reconnect connectors etc.
- Start the engine and let it idle.
- Read the lambda value for the rear Heated Oxygen Sensor (HO2S).

Note! It takes approximately 25 seconds before fuel trim starts.

Check that the value is within its permitted range. The value should be approximately 0.98 and 1.02.

If the value is now OK it means that the cause of the fault has been loose connections in connector.

Other information:
- To access/replace the heated oxygen sensor (HO2S), Heated Oxygen Sensor (HO2S), Replacing
- For information about signals, Pinout Values and Diagnostic Parameters

Is the value OK?
Yes - Testing Complete.
No - Continue below.


Checking wiring and components



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

Check signal cable (+) between control module # A42 and Heated Oxygen Sensor (HO2S) connector terminal 4 for an open-circuit according to [1][2]Checking Wiring and Terminals. Permanent Fault

Hint: With the ignition on and Heated Oxygen Sensor (HO2S) connector disconnected, the voltage between terminal 4 and ground terminal should be approximately 3.8 V.

Check signal cable (-) between control module # A41 and Heated Oxygen Sensor (HO2S) connector terminal 3 for an open-circuit according to [1][2]Checking Wiring and Terminals. Permanent Fault

If wiring is OK, try another heated oxygen sensor (11028).

Remedy as necessary.

Other information
- To access/replace the control module, Engine Control Module (ECM), Replacing
- To access/replace the heated oxygen sensor (HO2S), Heated Oxygen Sensor (HO2S), Replacing
- For information about signals, Pinout Values and Diagnostic Parameters


Verification



Hint: After carrying out the repair, check that the fault has been remedied.
- Ignition off.
- Reconnect connectors, reinstall components
- Start the engine and let it idle.
- Read the lambda value for the rear Heated Oxygen Sensor (HO2S).

Note! It takes approximately 25 seconds before fuel trim starts.

Check that the value is within its permitted range. The value should be approximately 0.98-1.02.

Is the value correct?
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.