P1171
CLOSED LOOP
Symptom Of Fault.
The CHECK ENGINE lamp (MIL) is on.
Any other diagnostic trouble codes (low fuel level misfiring, oxygen sensor, pressure sensor)
Conditions.
^ Coolant temperature above 60°C (140°F)
^ Closed loop active.
P1170: All-embracing DTC.
P1171: Closed loop > 25% for more than 20 sec.
P1172: Closed loop < -25% for more than 20 sec.
Diagnostic Help.
If the closed loop fault has arisen on account of low fuel level, this will be indicated by diagnostic trouble code P1416 also being generated.
Closed loop status can be ascertained by means of the ISAT scan tool.
- Select "READ FUNCTIONS".
- Select "LAMBDA CONTROL'.
Current closed loop status ± 25% will be displayed.
Checking The Wiring
Intermittent faults may occur as a result of occasional short circuits and breaks in the wiring. Jiggle the leads and in-line connectors at several places and in different directions to reveal faults in the wiring harness. Observe the multimeter, ISAT scan tool or test lamp while carrying out this check.
Diagnostic Procedure.
1. Check additional diagnostic trouble codes in the Trionic system
- Read out all the diagnostic trouble codes with the ISAT scan tool.
- P1416
- P0105-P0135
- P0441-P0445
Are any of the above diagnostic trouble codes present?
YES: Continue fault diagnosis for the relevant diagnostic trouble code.
NO: Continue with point 2.
NOTE: P1171 may be caused by misfiring.
2. Check for air leakage
- Check that no air leakage occurs at the following points:
^ the hose between the pressure sensor and intake manifold
^ the hose between the fuel pressure regulator and intake manifold
3. Check pressure sensor operation
- Turn the ignition switch to the ON position and then back to the OFF position.
- Connect an ISAT scan tool.
- Select "READ FUNCTIONS".
- Select "INTAKE PRESSURE".
The ISAT scan tool should show a reading of about 102 kPa (NOTE: the reading is dependent on air pressure).
First build up a pressure of 0.6 bar and then a create a vacuum of -0.6bar. Use a pressure gauge and a pressure/vacuum pump.
The ISAT scan tool should show 160 ± 5 kPa and 40 ± 5 (the ISAT scan tool may show somewhat lower readings at high altitude).
The measurement is intended to detect any shift in the operating range of the pressure sensor.
Are the readings OK?
YES: Continue with point 4.
NO: Change the pressure sensor and continue with point 6.
4. Check the front heated oxygen sensor's electrical interface
- Unplug the oxygen sensor's 4-pin connector.
- Replace the oxygen sensor with a conventional 1.5 V dry battery in good condition.
- Connect the battery's positive pole to pin 4 of the connector.
- Connect the battery's positive pole to pin 3 of the connector.
- Ignition switch in ON posit ' ion.
- Connect an ISAT scan tool.
- Select "READ FUNCTIONS".
- Select "O2S 1 ".
The ISAT scan tool must show approx. 1.4 V.
Does the ISAT scan tool show about "1.4 V"?
YES: Plug in the oxygen sensor and continue with point 5.
NO: Check the leads between pin 4 of the connector and pin 23 of the control module and between pin 3 of the connector and pin 47 of the control module for continuity and shorting. Rectify as necessary. Then continue with point 6.
5. Check
^ fuel pressure and flow
^ that the EVAP canister purge valve closes in the zero voltage state
^ that there is no air leakage in the exhaust system ahead of the front heated oxygen sensor or its mounting
Is there a relevant cause of the fault?
YES: Rectify the fault and proceed to point 6.
NO: Change the front heated oxygen sensor and continue with point 6.
6. Final check:
- Clear the diagnostic trouble code.
- Perform a driving cycle:
- Start the engine and run it at idling speed until the temperature of the coolant reaches 60°C (140°F).
- Run the engine at idling speed for another 5 minutes.
- Evaluation of the driving cycle: Check whether the diagnostic trouble code has recurred.
Has the diagnostic trouble code recurred?
YES: Continue at "Before Replacing a Control Module". Component Tests and General Diagnostics
NO: The remedial measure taken was correct.