Upper Limit
Upper limit
Checking ethanol content
Hint: The cause of the symptom and/or diagnostic trouble code may be that the vehicle has been refuelled with incorrect fuel for that vehicle. The fuel system contains fuel with too high ethanol content.
The energy content in ethanol-diluted fuel is lower than in pure gasoline. This means that the control module compensates for the lower energy content, by increasing the injection volume, to be able to reach lambda=1 at the front heated oxygen sensor. This compensation is normally called "Front lambda control slow" or "Lambda integrator", and varies to compensate for the vehicle's status in the form of component spread, small air leaks, wear, etc. The value of this compensation in the ideal case is 1.0 for pure gasoline. Increased ethanol content of the fuel increases the compensation by approx. 0.05 per 10% ethanol dilution.
The control module is designed to handle an ethanol dilution up to 25%. In combination with other deviations from the ideal case, however, lower ethanol content may be enough to cause customer symptoms. This mainly occurs at engine start with cool engine at outdoor temperatures below 0 °C. Then the diagnostic trouble code may also be set for the engine running on too lean mixture.
Note! In a vehicle intended for gasoline, only pure gasoline shall be used. Even if engine start/operation works, other fuel-related components in the vehicle may be damaged by too high ethanol content.
- Measure the ethanol content of the fuel according to the instructions below.
If measured ethanol content is above 25%, then ethanol dilution is the likely cause of the symptom and/or to the diagnostic trouble code being stored.
If measured ethanol content is below 25%, symptoms and/or diagnostic trouble code may have been caused by earlier occurrence of incorrect fuel in the system for that vehicle.
Hint: Check refuelling history by talking to customer.
If nothing indicates incorrect fuel, neither now nor earlier, continue troubleshooting to check other possible causes of faults.
Other information
- Measuring the ethanol content, B5254T7 Testing and Inspection
Continue - Checking the fuel injection system
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Checking the fuel injection system
Check the intake system for air leakage.
Hint: Air leakage in the intake system can occur through the canister purge (CP) valve, the secondary air solenoid valve and power brake booster.
Start the engine. Allow the engine to run at idle speed for 10 minutes.
Check the mass air flow (MAF) sensor. Read off its correction factor. The value must be between 0.8 and 1.2.
Note! There must not be any air leakage when this test is carried out.
Hint: If the above fault-tracing does not remedy the fault, try replacing the heated oxygen sensor (HO2S), as the diagnostic trouble code (DTC) can also be stored by a damaged heated oxygen sensor (HO2S).
Remedy as necessary.
Other information
- Air leaks in the intake system, checking Air Leaks In the Intake System, Checking
- Oxygen sensor (Catalyst monitor sensor), B5254T7 Service and Repair
Continue - Verification
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Verification
Verification
Read out and note the adaptation value.
Note! Do not erase diagnostic trouble codes (DTCs) as this also resets the adaptation values!
Test drive the car and perform a TRIP schedule.
Verifying repairs Verifying Repairs
Read off the fuel trim.
Check that the adaptation value is approaching 0 compared with the noted value. Check that the adaptation value is within the range 0 ±10 %.
Is the value OK?
Yes - VERIFIED
No - VERIFICATION FAILED
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VERIFICATION FAILED - Fault-tracing information
VERIFIED - FAULT FOUND
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Fault-tracing information
Attempt New Test - Checking the fuel injection system
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