Signal Too High. Permanent Fault
Signal too high. Permanent fault
EFI-121 Mass air flow (MAF) sensor
Checking power ground
- Ignition off.
- Wait for approximately 150 seconds (cars with immobilizer 245 seconds).
- Disconnect mass air flow (MAF) sensor.
Connect an ohmmeter between mass air flow (MAF) sensor connector terminal 1 and ground.
The ohmmeter should read approximately 0 ohms.
OK - Checking signal ground
Not OK - Checking control module connector
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Checking control module connector
- Ignition off.
- Mass air flow (MAF) sensor disconnected.
- Check control module connector for contact resistance and oxidation and remedy according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
- Control module connected.
Connect an ohmmeter between mass air flow (MAF) sensor connector terminal 1 and ground.
The ohmmeter should read approximately 0 ohms.
OK - Checking signal ground
Not OK - Check cable between mass air flow (MAF) sensor terminal 1 and engine control module (ECM) #A3 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 1 and engine control module (ECM) #A3 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 signal ground
- Ignition off.
- Mass air flow (MAF) sensor disconnected.
Connect an ohmmeter between mass air flow (MAF) sensor connector terminal 2 and ground.
The ohmmeter should read approximately 0 ohms.
OK - Checking the signal cable
Not OK - Checking control module connector
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Checking control module connector
- Ignition off.
- Mass air flow (MAF) sensor disconnected.
- Check control module connector for contact resistance and oxidation and remedy according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
- Control module connected.
Connect an ohmmeter between mass air flow (MAF) sensor connector terminal 2 and ground.
The ohmmeter should read approximately 0 ohms.
OK - Checking the signal cable
Not OK - Check cable between mass air flow (MAF) sensor terminal 2 and engine control module (ECM) #A5 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 2 and engine control module (ECM) #A5 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 on.
- Mass air flow (MAF) sensor disconnected.
Connect a voltmeter between mass air flow (MAF) sensor connector terminal 4 and ground.
Voltmeter should read 0 - 1 V.
OK - Checking mass air flow (MAF) sensor signal
Not OK - 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 supply voltage according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault. After remedying fault continue with Checking mass air flow (MAF) sensor.
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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 supply voltage according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Continue - Checking mass air flow (MAF) sensor
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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 2 and 4.
Voltmeter should read 0.1 - 0.2 V.
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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Checking mass air flow (MAF) sensor
- The mass air flow (MAF) sensor may fail if there has been a short-circuit to supply voltage in the signal cable. Check mass air flow (MAF) sensor as follows:
- Ignition off.
- Connect mass air flow (MAF) sensor.
- Ignition on.
Connect a voltmeter between mass air flow (MAF) sensor connector terminals 2 and 4.
Voltmeter should read 0.1 - 0.2 V.
OK - Mass air flow (MAF) sensor is OK. Then continue with Verification.
Fault-tracing information
Not OK - Try a new mass air flow (MAF) sensor. Then continue with Verification.
Replacing component
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Fault-tracing information
Mass air flow (MAF) sensor is OK.
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 power ground
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