Signal Too High. Permanent Fault

Signal too high. Permanent fault

EFI-521 Front heated oxygen sensor (HO2S), preheating EFI-522 Rear heated oxygen sensor (HO2S), preheating

Checking the signal cable








- Ignition off.
- Disconnect heated oxygen sensor (HO2S) (front heated oxygen sensor (HO2S): black connector, rear heated oxygen sensor (HO2S): gray connector).
- Ignition on.
Connect a voltmeter between the heated oxygen sensor (HO2S) connector terminal 2 (engine control module (ECM) side) and ground.









The voltmeter should read approximately 0 V.

OK - Try a new heated oxygen sensor (HO2S). Then continue with Verification.
Replacing component

Not OK - Check cable between heated oxygen sensor (HO2S) terminal 2 and engine control module (ECM) #A14 (for diagnostic trouble code (DTC) EFI-521)/ #A29 (for diagnostic trouble code (DTC) EFI-522) for a short-circuit to supply voltage according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault. Then continue with Verification.
Checking for a short-circuit

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Replacing component
- Try a new heated oxygen sensor (HO2S).





Continue - Verification

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Checking for a short-circuit








- Check cable between heated oxygen sensor (HO2S) terminal 2 and engine control module (ECM) #A14 (for diagnostic trouble code (DTC) EFI-521)/ #A29 (for diagnostic trouble code (DTC) EFI-522) for a short-circuit to supply voltage according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.

Continue - Verification

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Verification




Verification

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












- Ignition off.
- Front and rear heated oxygen sensors (HO2S) connected.
- Control module connected.
- Disconnect the Volvo Scan Tool (ST) from the VIDA station and use it in stand-alone mode.
- Start the engine and idle it.
- Go into verification menu.
Watch the diagnostic trouble code (DTC) to be verified.
Wait until its status switches to tested
This can take up to 5 minutes for EFI-521.
This can take up to 15 minutes for EFI-522.
- Read off diagnostic trouble codes (DTCs).

If EFI-521 or EFI-522 are stored they should intermittent fault status.

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

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 - Checking the signal cable

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