How accurate are the EEC-IV diagnostics ?
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Freshman User
Joined: Apr 2003
Posts: 45
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From: Long Island, NY
How accurate are the EEC-IV diagnostics ?
Hi All-
I've read many threads with advice about diagnosing a problem. The experts all agree that the first thing you have to do is 'pull the codes". And after that if all is well, then you have to do fuel pressure tests and specific tests on the TFI ignition etc. My question is, how reliable are the diagnostics ? If the diags say that the TPS ( throttle position sensor) is OK, how many times have folks replaced it and found that it made a difference in the way the engine ran, even after diags said it was OK ? Or if the diags said that the ECT (engine coolant temp) sensor was OK and then they replaced it and it made a difference. Reason I ask is that on one of the 'gas mileage' threads someone said that they replaced the TPS and it made a difference and then when on to say that the diags said it was OK.
I've read many threads with advice about diagnosing a problem. The experts all agree that the first thing you have to do is 'pull the codes". And after that if all is well, then you have to do fuel pressure tests and specific tests on the TFI ignition etc. My question is, how reliable are the diagnostics ? If the diags say that the TPS ( throttle position sensor) is OK, how many times have folks replaced it and found that it made a difference in the way the engine ran, even after diags said it was OK ? Or if the diags said that the ECT (engine coolant temp) sensor was OK and then they replaced it and it made a difference. Reason I ask is that on one of the 'gas mileage' threads someone said that they replaced the TPS and it made a difference and then when on to say that the diags said it was OK.
Posting Guru
Joined: Jul 2003
Posts: 2,232
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From: Colville, Washington
The ECM can only report readings "out of range". For example on a '95 F150 with 5.0L, check engine light came on while driving with a noticeable drop in power. Codes indicated TPS reading higher than expected and O2 sensor shows lean condition. Most people would replace the TPS and O2, however if you think of the relationship between the two codes, you will see the throttle was open farther than it should be for RPM of engine and it is still running lean...
I replaced the fuel filter, it was at least 70,000 miles old, and the truck runs like a champ...no more codes.
The ECM can and does compensate to a point for worn or slightly out of spec readings also, so a sensor might not be "right" but still within the ECM's parameters to function without a CEM.
I replaced the fuel filter, it was at least 70,000 miles old, and the truck runs like a champ...no more codes.
The ECM can and does compensate to a point for worn or slightly out of spec readings also, so a sensor might not be "right" but still within the ECM's parameters to function without a CEM.
