DTC 1-2-1

EC. Diagnostic trouble code (DTC) 1-2-1 MFI LH 2.4

* 1-2-1 Mass air flow (MAF) sensor signal absent or faulty



DTC conditions:
If the signal from the MAF sensor to the control module is faulty or absent, the control module will not receive Information about the volume of air passing into the engine. This information is needed so that the correct quantity of fuel can be injected. The control module posts a DTC and goes into limp home mode. This has fixed injection times making It possible to drive the car.

Causes of fault:
Open circuit or short circuit to GND in wiring, connector or MAF sensor.

Fault symptoms:
Various driving problems, high fuel consumption.

EC1




Resetting diagnostic trouble codes (DTCs)
- Read and delete the DTCs.
- Start the engine and let it run for about a minute.

If the DTC recurs:
^ Check the GND EC2.

If the DTC does not recur:
Intermittent fault.
^ Check the MAF sensor connections and wiring for loose contacts in accordance with NA5 and clean the MAF sensor connector and treat it for corrosion in accordance with NA7. NA. Checking the Wiring

EC2




Check GND
- Ignition off.
- Disconnect the connector from the MAF sensor.
Connect an ohmmeter between connector terminal 1 and GND.
The ohmmeter should read 0 ohms.

If this value is OK:
^ Check the power supply EC3.

If the reading is incorrect:
^ Check the wiring to the MAF sensor for breaks or contact resistance in accordance with NA2 and NA6. NA. Checking the Wiring

EC3




Checking power supply
- Ignition on.
Connect a voltmeter between terminal 5 on the MAF sensor connector and GND.
The voltmeter should read battery voltage.

If this value is OK:
^ Check the MAF sensor EC4.

If the reading is approx. 0 V:
^ Check the wiring between terminal 5 on the MAF sensor and the system relay for breaks in accordance with NA5 and clean the MAF sensor connector and treat it for corrosion in accordance with NA7. NA. Checking the Wiring

EC4




Checking the Mass Air Flow (MAF) sensor
- Reinstall connector.
- Ignition on.
Connect a voltmeter between terminal 3 on the MAF sensor and GND.
The voltmeter should read 1.4 V.

If this value is OK:
^ Connect test box EC5.

If the reading is incorrect:
- Clean the MAF sensor connector and treat it for corrosion in accordance with NA7. NA. Checking the Wiring
- Install the connector.
- Repeat the measurement.
^ If the reading is still incorrect try using a new MAF sensor.

EC5




Connecting the test box
Connect the test box to MFI and check GND points in accordance with P1-P2. P. Test Box, Signal Description
^ Continue with Checking the signal wiring EC6.

EC6




Checking the signal wiring
- Ignition off
- Disconnect connector
Connect an ohmmeter between #7 and #5.
The ohmmeter reading should indicate infinite resistance.

If this value is OK:
^ Check the signal level EC7.

If the reading is 0 ohms:
^ Check the wiring between MAF sensor connector terminal #3 and #7 in the control module for grounding in accordance with NA3. NA. Checking the Wiring

EC7




Checking the signal level
Connect the control module.
- Connect the connector.
- Insert fuse 1 (or 31).
Connect an voltmeter between #7 and #5.
The voltmeter should indicate the save reading as in EC3 (1.4V).

If this value is OK:
Intermittent fault.
^ Check the wiring and connections for loose contacts In accordance with NA5. NA. Checking the Wiring

If the reading deviates:
^ Check the wiring between MAF sensor connector terminal 3 and #7 in the control module for breaks in accordance with NA3. NA. Checking the Wiring