TR. MFI#33
MFI#33 No idle air control (IAC) valve signal
Fault Message Conditions:
The fault message is logged if voltage is below 2.5 V for 300 ms.
Causes of fault:
Break or grounding between MFI#33 and the valve.
Break or grounding in the IAC valve.
Fault symptoms:
Low idle speed.
TR1
Volvo ST, Test Box
-Disconnect the ST in accordance with QA2. Connecting The Volvo Scan Tool (ST)
Connect the test box to MFI and check the GND points in accordance with P1-P2.
-Continue with Checking the wiring and valve resistance.
TR2.
Checking The Wiring And Valve Resistance
-Ignition off.
Connect an ohmmeter between MFI#33 and MFI#9.
The ohmmeter should read approx. 8 OHMS.
If this value is OK
-Check the wiring's resistance to GND TR3.
If the reading is incorrect
-Check the valve resistance TR6.
TR3
Checking The Wiring's Resistance To GND
-Ignition off.
-Disconnect the IAC valve.
Connect an ohmmeter between MFI#33 and MFI#5 (GND). The ohmmeter should read infinite resistance.
If this value is OK
-Check the signal to valve TR4.
If the reading deviates
-Check the wiring between the control modules for grounding in accordance with NA3. Checking the Wiring
TR4
Checking The Power Supply
-Connect the control module to the test box.
-Connect the IAC valve
-Install the fuse.
-Ignition on.
Connect a voltmeter between MFI#33 and MFI#5 (GND).
The voltmeter should read battery voltage.
If this value is OK
-Check the control of #33 TR5.
If the reading deviates
-Check the wiring between MFI#33 and the valve and between MFI#9 and the valve for breaks in accordance with NA2. Checking the Wiring
TR5
Checking Control #33
-Start the engine and let it idle. The voltmeter should read 7-10 V.
If this value is OK
Intermittent fault.
-Check the connections for loose contacts in accordance with NA5. Checking the Wiring
If the voltage does not drop
-Try using a new control module.
TR6
Checking The Valve Resistance
-Ignition off.
-Disconnect the IAC valve.
Connect an ohmmeter between terminals 1 and 2 on the valve. The ohmmeter should read approx. 8 OHMS.
If this value Is OK:
-Check the wiring between MFI#33 and the valve and the wiring between MFI#9 and the valve for breaks. Checking the Wiring
If he reading Is incorrect:
-Try using a new IAC valve.