DTC 2-2-1

2-2-1 LONG TERM FUEL TRIM, PART LOAD




Trouble Code Conditions
The control module receives information from the Heated Oxygen Sensor (HO2S) on the fuel/air mixture in idle and part load ranges. If the fuel/air mixture deviates, the short term fuel trim will compensate for this by adjusting injection period. When the short term fuel trim makes an adjustment, the adaption must adjust its mid point. When the adaption has to adjust near to maximum, a Diagnostic Trouble Code (DTC) is set.

Substitute value(s)
- None.

Fault source(s)
Upper limit:
- Defective Mass Air Flow (MAF) sensor.
- Air leakage.
- Low fuel pressure.
- Faulty sensor signals.

Lower limit:
- Defective Mass Air Flow sensor.
- High fuel pressure.
- Leaking injection valves.
- Leaking EVAP system.
- Contaminated engine oil.
- Oil level too high.
- Faulty sensor signals.

Fault symptom(s)
- High fuel consumption.
- Poor performance.

TEST PROCEDURE




STATUS REPORT
- Upper limit.
^ Proceed to: UPPER LIMIT section below.

- Lower limit.
^ Proceed to: LOWER LIMIT section below.

UPPER LIMIT
Check load signal
- Start engine.
- Gear selector: neutral, AC: off and engine warm.
- Power consumers such as engine coolant fan, heated rear window etc.: off.
- Enter DTC parameter list.



- Read off values of load signal.

Values should be 2.3 - 2.4 volts at idle.

If values OK:
^ Check air leakage in intake system. Proceed to CHECK AIR LEAKAGE IN INTAKE SYSTEM section below.

If values differ:
^ Test with new MAF sensor.

CHECK AIR LEAKAGE IN INTAKE SYSTEM
- Check for air leakage.
- Check air leakage in intake system.

If no air leakage detected:
^ Check fuel and residual pressure. Proceed to CHECK FUEL AND RESIDUAL PRESSURE section below.

If air leakage detected:
^ Fix as necessary.
^ Erase DTCs.




CHECK AIR LEAKAGE IN EXHAUST SYSTEM
- Check for air leakage.
- Check air leakage in exhaust system.

If no air leakage detected:
^ Check fuel and residual pressure. Proceed to CHECK FUEL AND RESIDUAL PRESSURE section below.

If air leakage detected:
^ Fix as necessary.
^ Erase DTCs.




CHECK FUEL AND RESIDUAL PRESSURE
- Check fuel and residual pressure.

If fuel and residual pressure OK:
^ Connect breakout box. Proceed to CONNECT BREAKOUT BOX section below.

If fuel and residual pressures differ:
^ Fix as necessary.
^ Erase DTCs.




CONNECT BREAKOUT BOX
- Connect breakout box and check control points.
- Connect ECM.
- Check all signals to and from ECM.
- Fix as necessary.
- Erase DTCs.




LOWER LIMIT
Check load signal
- Start engine.
- Gear selector: neutral, A/C: off, engine warm.
- Enter DTC parameter list.
- Read off values of load signal.

Values should be 2.3 - 2.4 volts at idle.

If values OK:
^ Check fuel and residual pressure. Proceed to CHECK FUEL AND RESIDUAL PRESSURE section below.

If values differ:
^ Check with a new MAF sensor.




CHECK FUEL AND RESIDUAL PRESSURE
- Check fuel and residual pressure.

If fuel and residual pressures are OK:
^ Check EVAP valve. Proceed to CHECK EVAP VALVE section below.

If fuel and residual pressures differ:
^ Fix as necessary.
^ Erase DTCs.




CHECK EVAP VALVE
- Remove hose connecting intake manifold and EVAP valve.
- Refit hose after fault tracing. For refitting, use pliers 981 4215 and a new hose clip.
- Connect vacuum pump 999 5843 to EVAP valve connection.

NOTE: When a vacuum is achieved, the vacuum meter should show a stable reading.

If valve is OK:
^ Check engine oil level. Proceed to CHECK ENGINE OIL LEVEL section below.

If valve is faulty:
^ Test with a new EVAP valve.
^ Erase DTCs.




CHECK ENGINE OIL LEVEL
- Check engine oil level.
- Oil level should be between minimum and maximum marks.

If oil level OK:
^ Check engine oil. Proceed to CHECK ENGINE OIL section below.

If oil level incorrect:
^ Fill to correct level. Check engine oil. Proceed to CHECK ENGINE OIL section below.




CHECK ENGINE OIL
- Start engine and allow to idle for a few minutes.
- Enter DTC parameter list.
- Read off HO2S values and note.
- Disconnect and plug crankcase ventilation system.
- Read off HO2S values again.

Values should be more or less the same.

If values OK:
^ Connect breakout box. Proceed to CONNECT BREAKOUT BOX section below.

If values differ:
^ Engine oil is contaminated with fuel. Change oil and oil filter.
^ Erase DTCs.




CONNECT BREAKOUT BOX
- Connect breakout box and check control points.
- Connect ECM.
- Check all signals to and from ECM.
- Fix as necessary.
- Erase DTCs.