Has replacement ECM ever solved a problem?

XJ40
1

I have struggled with a Fuel Fail 89 (purge valve) for quite some time (years). I have gone through the testing procedure as outlined in the Engine Management System Diagnostic Guide multiple times as well confirming that most other emission controls items are working correctly. All grounds have been thoroughly cleaned. And the bottom line: the ECM does not seem to be switching the ground for the purge valve.

The diagnostic guide says to replace the ECM under such conditions but I am hesitant to do so given the cost along with the possibility that something else may be causing the ECM to not switch the purge valve correctly.

And so my question: Has anyone actually solved a problem by replacing the ECM? Are they prone to failure? Is it safe to assume that a 1990 AJ6 being pre-OBD1 doesn’t need to be programmed by the dealer if the numbers match the original ECM?

2

I would assume similar year/engine size ECM’s are interchangeable with out dealer interference.

3

I had a 4.0 liter 1990 XJ40 that had a PERMANENT FF37. The output semiconductor in the ECM was faulty as a replacement ECM fixed it and the old ECM had the fault follow to another car.

The other car had NO FAULTS but the FF37 showed up when the faulty ECM was installed temporarily.

Yes, the ECM can have faulty outputs to solenoids and valves.

The first two years of the XJ40 should be 3.6 so any ECM from them should interchange.