Function Check

EJ. Diagnostic Trouble Code (DTC) 2-1-2 MFI LH 2.4 And LH 3.1

Heated oxygen sensor (HO2S) signal absent or faulty

If DTC 2-1-2 is logged at the same time as other DTCs, the first code to be presented by the OBD system should be remedied first. The following DTCs are regarded as secondary faults.





DTC Conditions:

If the signal is absent the control module cannot handle

HO2S control. A DTC is logged if the signal is faulty (over

1.1 V) or absent (0.5 V), 3 minutes after engine temperature has exceeded 80°C (176°F).

Causes of fault:

Breaks, short circuits in the HO2S wiring. Contact resistance in connections. No pre-heating of the HO2S.

Fault symptoms:

High fuel consumption, can cause driving problems.

EJ1

Checking The Signal From The Heated Oxygen Sensor (H025)




-Start and warm up the engine.

Connect a voltmeter between terminal 1 (1-pole connector at the firewall) and GND.

The voltmeter reading should fluctuate between 0.1-0.9 V.

1. If the reading is OK:

Intermittent fault.

-Check the wiring for loose contacts, If no faults are detected, connect the ST.

2. If the reading is constant approx. 0.5 V:

-Check the HO2S pre-heater EJ6.

If the reading is constant approx 0 V:

-Check the HO2S reference voltage

If the reading is constant over 1.0 V:

-Check the HO2S reference voltage EJ2.

EJ2

Checking The Heated Oxygen Sensor (HO2S) Reference Voltage




-Ignition on.

-Disconnect the HO2S 1-pole connector.

Connect a voltmeter between the 1-pole connector (by the control module) and GND.

The voltmeter should read approx. 0.5 V.

If this value is OK:

-Check the MAF sensor GND point EJ8.

If the reading is approx. 0 V:

-Connect the test box.

If the reading is over 1 volt:

-Check the wiring between MFI #24 and the HO2S for short circuits.

When the fault has been remedied:

-Check the signal from the HO2S in accordance with EJ1.

EJ3

Connecting The Test Box




Connect the test box to MFI LH 2.4/LH 3.1 and check the GND points in accordance with P1-P2.

-Continue with Checking the signal wiring EJ4.

EJ4

Checking Signal Wiring





-Ignition off

Connect an ohmmeter between #24 and #5.

The ohmmeter should read infinite resistance.

If this reading is OK:

-Check the resistance in the wiring EJ5.

If the reading is 0 OHMS.

-Check the wiring to control module #24 for grounding.





EJ5

Checking The Resistance In The Wiring

Connect an ohmmeter between #24 and the 1-pole connector at the firewall (by the control module).

The ohmmeter should read 0 OHMS.

If this value is OK:

-Try using a new control module.

If resistance is infinite:

-Check the wiring to control module #24 for breaks.

EJ6

Checking The Heated Oxygen Sensor (HO2S) Preheater




-Engine running.

Connect a voltmeter between terminal 1 and GND in the 2-pole connector.

The voltmeter should read battery voltage.

If this value is OK:

-Check the GND point EJ7.

If the reading is approx. 0 V:

-Check the wiring between fuse 4 and the connector for breaks.

EJ7

Checking The GND Point




-Engine running.

Connect a voltmeter between terminals 1 and 2 in the HO2S 2-pole connector.

The voltmeter should read approx 12 V.

If this value is OK:

-Check the MAF sensor CND point EJ8.

If the reading is Incorrect:

-Check the wiring to the GND point for breaks.

EJ8

Checking The Mass Air Flow (MAF) Sensor GND Point

-Ignition off.

-Disconnect the connector from the MAF sensor.




LH 2.4: Connect an ohmmeter between terminal 1 in the MAF sensor connector and GND.




LH 3.1: Connect an ohmmeter between terminal 2 in the MAF sensor connector and GND.

The ohmmeter should read 0 OHMS.

If this value is OK:

-Check the MAF sensor signal EJ9.

If the reading is incorrect:

-Check the wiring to the GND point for contact resistance in the intake manifold GND point.

EJ9

Checking The Mass Air Flow (MAF) Sensor Signal

-Clean the MAF sensor connector and treat it for corrosion.

-Install the connector.

-Start the engine.




LH 2.4: Connect a voltmeter between 3 (on the back of the MAF sensor connector) and GND.

The voltmeter should read approx. 2.3 V.




LH 3.1: Connect a voltmeter between 4 (on the back of the MAF sensor connector) and GND.

The voltmeter should read approx. 3.5 V.

If this value Is OK:

-Try using a new HO2S.

If the reading is incorrect:

-Replace the MAF sensor and repeat the readings.