Signal Too Low. Permanent Fault
Signal too low. Permanent fault
EFI-121 Mass air flow (MAF) sensor
Checking fresh air intake
- Ignition off.
Check that the fresh air intake is intact and properly connected.
Is the fresh air intake intact?
Yes - Checking power cable
No - Remedy as necessary. Then continue with Verification.
Corrective action
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Corrective action
- Remedy as necessary.
Continue - Verification
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Checking power cable
- Ignition off.
- Disconnect mass air flow (MAF) sensor.
- Ignition on.
Connect a voltmeter between mass air flow (MAF) sensor connector terminal 3 and ground.
The voltmeter should read battery voltage.
OK - Checking the signal cable
Not OK - Check cable between mass air flow (MAF) sensor terminal 3 and main relay (2/32) terminal 3 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault. Then continue with Verification.
Checking for an open-circuit
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Checking for an open-circuit
- Check cable between mass air flow (MAF) sensor terminal 3 and main relay (2/32) terminal 3 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - Verification
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Checking the signal cable
- Ignition off.
- Wait for approximately 150 seconds (cars with immobilizer 245 seconds).
- Mass air flow (MAF) sensor disconnected.
Connect an ohmmeter between mass air flow (MAF) sensor connector terminal 4 and ground.
The ohmmeter should read approximately 9 - 11 kohms.
OK - Checking mass air flow (MAF) sensor signal
Low - Check cable between mass air flow (MAF) sensor terminal 4 and engine control module (ECM) #A4 for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault. Then continue with Verification.
Checking for a short-circuit
High - Check cable between mass air flow (MAF) sensor terminal 4 and engine control module (ECM) #A4 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault. Then continue with Verification.
Checking for an open-circuit
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Checking for a short-circuit
- Check cable between mass air flow (MAF) sensor terminal 4 and engine control module (ECM) #A4 for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - Verification
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Checking for an open-circuit
- Check cable between mass air flow (MAF) sensor terminal 4 and engine control module (ECM) #A4 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - Verification
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Checking mass air flow (MAF) sensor signal
- Ignition off.
- Connect mass air flow (MAF) sensor.
- Ignition on.
Connect a voltmeter between mass air flow (MAF) sensor connector terminals 4 and 2.
The voltmeter should read approximately 0.1-0.2V.
OK - The cause of the diagnostic trouble code (DTC) has been loose connections in the mass air flow (MAF) sensor and/or the engine control module (ECM) connectors. Check connectors for contact resistance and oxidation and remedy in accordance with Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault. Then continue with Verification.
Checking for contact resistance and oxidation
Not OK - Try a new mass air flow (MAF) sensor. Then continue with Verification.
Replacing component
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Checking for contact resistance and oxidation
The cause of the diagnostic trouble code (DTC) has been loose connections in the mass air flow (MAF) sensor and/or the engine control module (ECM) connectors.
- Check connectors for contact resistance and oxidation and remedy in accordance with Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - Verification
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Replacing component
- Try a new mass air flow (MAF) sensor.
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.
- Reinstall connectors, components etc.
- Start the engine and idle it for a minute.
Read off any diagnostic trouble codes (DTCs).
If EFI-121 is stored they should have intermittent 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 fresh air intake
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