TM. MFI #24 Heated Oxygen Sensor (HO2S) Signal Faulty

TM. MFI #24

MFI#24 Heated oxygen sensor (HO2S) signal faulty




Fault message conditions:
The fault message is logged lithe voltage difference between high and low signals has been less than 0.3 V for more than 10 seconds.
This measurement is not carried out if engine speed is above 2500 rpm, the idle switch is closed, the fuel is shut off or the engine temperature is under 70°C (158°F).

Causes of fault:
Grounding or voltage in the wiring between MFI#24 and HO2S.
Break in the wiring to the HO2S power supply.

Fault symptoms:
High fuel consumption.

Note: When checking wiring, the ST should be disconnected in accordance with QA2. QA. Connecting The Volvo Scan Tool (ST)

TM1




Monitor Test
- Check the HO2S signal in Monitor Test.
The signal should vary between low signal (<0.2V) and high signal (>0.7 V) about every other second.

If the signal is OK
^ check the connections for loose contacts in accordance with NA3.

If the signal Is a constant approx. 0 V
^ check the wiring between MFI#24 and H028 for grounding in accordance with NA3. NA. Checking the Wiring

If the signal is a constant 0.5 V
^ On 740/940 with B200F/FB, B230 F/FB, B234F check wiring between HO2S sensor fuse 11 for open circuit in accordance with NA2. NA. Checking the Wiring
^ On 760/960 with B230FT check wiring between HO2S sensor and the solderpoint for open circuit in accordance with NA2. NA. Checking the Wiring
^ On 740/940 with B230FT check wiring between HO2S sensor and terminal 5 on main relay for open circuit in accordance with NA2. NA. Checking the Wiring

If the signal is a constant 1.0 V or over
^ check the wiring between MFI#24 and the HO2S for short circuits in accordance with NA4. NA. Checking the Wiring