Upper Limit

ECM-250A LONG-TERM FUEL TRIM
UPPER LIMIT

Checking fuel injection system



Check the intake system for air leakage according to Check For Air Leaks In the Intake System

Hint: Air leakage in the intake system may occur through the canister purge (CP) valve and the power brake booster for example.

Check the fuel pressure according to Checking Fuel and Residual Pressures

Check the mass air flow (MAF) sensor: Read the mass air flow at different engine speeds. Mass Air Flow (MAF) Sensor

Note! There must not be any air leakage when this test is carried out.

Remedy as necessary.

Other information:
- To access/replace the mass air flow (MAF) sensor, Mass Air Flow (MAF) Sensor, Replacing


Incorrect adaptation range



- Engine running.
- Check and note which adaptation range is incorrect.

This makes it possible to start the engine later and run it in the range which caused the diagnostic trouble code (DTC).

Hint: The normal value should be between 0.90 - 1.10.


Reset adaptations



- Switch off the engine.
- Ignition on.
- This is so that the system can be started from normal. As a result, it is easier to see if an adaptation is going up or down.


Start adaptations



Start and run the engine in the faulty adaptation range until the value is stable.
Check that the adaptation value is between 0.90 - 1.10.

Certain conditions must be met for adaptation to start
- engine speed (RPM) [ge] 600 rpm
- engine coolant temperature (ECT) between 80 - 110°C
- air flow (according to table) (see the table below for the mass air flow parameters for an active adaptation)
- adaptation active = executed
- canister purge (CP) valve not active = 0 [mu]s.

Hint: If fuel vaporization is high, the canister purge (CP) valve is active for long periods. In this case, it may be necessary to disconnect the hose between the canister purge (CP) valve and the EVAP canister.

Hint: Parameters above level 2 can be difficult to achieve in the workshop with no load on the engine.

mass air flow parameter level 1 above 2 g/s below 7.5 g/s
mass air flow parameter level 2 above 7.5 g/s below 11.5 g/s
mass air flow parameter level 3 above 11.5 g/s below 15.5 g/s
mass air flow parameter level 4 above 15.5 g/s below 19.5 g/s
mass air flow parameter level 5 above 19.5 g/s

Is the adaptation value between 0.90 and 1.10?
Yes - Testing Complete.
No - Continue below.


Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt