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Discussion Starter #1
I have a 95 f150 xlt 351w. Had the motor changed (same motor less miles).

Im getting a check engine light only once i start driving. Goes away after truck is shut off. No blinking no other lights. Seems to only effect the shifting of the tranny.

Any other fixes then a ecu reflash? And if so where would i have that done in the southern NY area?

TIA for any help
 

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Welcome to the FFO!

Pull codes first.
AutoZone O'Reilys or many fast moving parts store will do for free

Post the codes
Re-flashing the PCM (or changing the software program) is generally not needed.

How long ago was the engine replaced?
Were electronic engine parts replaced as well?
Or was it just bare engine pieces?

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Only bare engine was replaced had a shop try to read codes two of their computers wouldnt read it. Obd1 part stores dont care those computers
 

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Oh I missed the year. The system is EEC IV.

The codes can be pulled with a voltmeter. However by the 1990s there were 3 digit codes. Which are kind of hard to see/count on a volt meter.
A Star tester or a New Generation Star tester takes the guess work out.

Reprogramming (reflashing) an EEC IV doesn't work the same because of the way the data is handled. You would have to get a chip or turner kit to monitor what is happening and how the program changes are working.

If no electronics were replaced, either something is not connected correctly or an existing sensor or actuator has failed or is partially failed. (Like an O2 sensors sending signals that do not make sense) Pulling codes is the way to find out what is going on.
Sounds like an intermittment fault and that will be stored in memory.

Why was the engine replaced?

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An easy thing to do would be to reset.
Disconnect the battery for an hour and then reconnect.
(Can be done with a reader but this is a cheap way)
May not accomplish what you want but it won;t hurt anything.

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The motor was replaced cause it threw a bearing and had 193000 miles on it.
 

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If the oxygen sensors have not been replaced I would do that as a maintenance item.

Then you need to find a Star tester or some one that has one.

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Ok so update... now im puzzled really thinking ecu issue... no cel even when key is in on position. I get battery light comes on and the airbag light flashes. But no cel at all sat 5 mins waiting. Got nothing.
 

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Key on engine off the CEL warning lamp should come on at least for a brief period of time as a check to make sure the light bulb works. (This is true of all warning lights) If it does not come on then the bulb would be suspect. As in the bulb is burned out.

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The bulb is fine. I know this cause as soon as i start to drive the light comes on. But key on engine off there is no light
 

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Im picking up my star tester today hopfully some answers come with it. Ill update once i read the codes thanks for the help
 

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Ok update. I ran two diagnostics tests today....

Key on engine off... no codes.

Key on engine running and i got 6 codes.

121, 172, 332, 538, 536, 632

Anyone deal with these codes before? Reminder its 95 f150 351w.
 

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Lambda sensor is an oxygen sensor. If the O2 sensors are throwing codes they are way beyond useful. As you notes show they are cheap and easy. A rare combo in automotive maintenance. Generic are perectly fine as they all work the same. Only the wire count and connector type is important.

The smog pump does not work with EGR. Those are two seperate systems. The insufficient flow is based on a sensor on top of EGR valve. That sensor is not picking up the EGR valve is moving. Either because the sensor is bad or the EGR is stuck. Given the age of the vehicle I would replace both. The EGR system is supposed to operate under warm engine and vehicle at speed. May be the reason for CEL to come on and off.



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