Computer sensor problem
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Computer sensor problem
I have a 1990 F-250 with a 5.8engine. I changed anti-freeze following the owner’s manual: drain, flush, put new in, start, run until upper hose warm, shut off and top off with fluid. I did this and now the truck will not start. I now have error codes:
21 Engine Coolant Temperature sensor signal voltage out of range.
24 Air Charge Temperature sensor signal voltage is out of specification.
26 Mass Air Flow sensor signal voltage out of Self-Test specifications.
I did a voltage test on the ECT and ACF and they are both around 3.0 volts. According to the Haynes repair manual they should be around 5.0 volts.
I put a new Engine Coolant Temperature sensor in and had no results.
Help!
21 Engine Coolant Temperature sensor signal voltage out of range.
24 Air Charge Temperature sensor signal voltage is out of specification.
26 Mass Air Flow sensor signal voltage out of Self-Test specifications.
I did a voltage test on the ECT and ACF and they are both around 3.0 volts. According to the Haynes repair manual they should be around 5.0 volts.
I put a new Engine Coolant Temperature sensor in and had no results.
Help!
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
Many of the sensors require the engine to be fully warmed up before they will test properly. The PCM assumes everything is warm. So when you ran the test, it saw the ECT was out of range - of course it was. The engine is cold. There was nothing wrong with the old one.
You said it won't start, but we need more information. What does it do? Turn over but not catch? Not turn over? Sometimes the underhood light can drain a weak battery while you're working under the hood. Any chance the battery is just dead?
You said it won't start, but we need more information. What does it do? Turn over but not catch? Not turn over? Sometimes the underhood light can drain a weak battery while you're working under the hood. Any chance the battery is just dead?
Posting Guru
Joined: Sep 2002
Posts: 2,420
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From: Langhorne, PA
When you were flushing the engine did you keep the water under control, or did it splash around the engine bay?? If you got some electronics wet or water in the distributor cap, that may kill an engine.
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Originally Posted by andym
Many of the sensors require the engine to be fully warmed up before they will test properly. The PCM assumes everything is warm. So when you ran the test, it saw the ECT was out of range - of course it was. The engine is cold. There was nothing wrong with the old one.
You said it won't start, but we need more information. What does it do? Turn over but not catch? Not turn over? Sometimes the underhood light can drain a weak battery while you're working under the hood. Any chance the battery is just dead?
You said it won't start, but we need more information. What does it do? Turn over but not catch? Not turn over? Sometimes the underhood light can drain a weak battery while you're working under the hood. Any chance the battery is just dead?
The battery was charged up and tested as a possible problem, the battery is fine. I checked for loose connections (ok) and the fuel pump is working. Spark plugs, wires, and distributer are all less then six months old, and couldn't fine any loose connections.
I was also careful with the coolant and none was splashed on the engine or electrical.
The starter turns the motor over but the motor doesn't catch or run.
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Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
The codes don't indicate a problem at all, so it's got to be something simple.
- How did you test for spark and fuel?
- Are you sure you didn't bump the distributor a little? If the hold down bolt is loose and it moved a little, it won't start. Just one possibility.
- Did you splash too much water on anything? Like the distributor? If it gets water inside it, the truck won't run until it get dried out.
- How did you test for spark and fuel?
- Are you sure you didn't bump the distributor a little? If the hold down bolt is loose and it moved a little, it won't start. Just one possibility.
- Did you splash too much water on anything? Like the distributor? If it gets water inside it, the truck won't run until it get dried out.
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Thanks.
I checked the entire starting system and found a faulty wire from the distributor to the coil. It was replaced and the truck runs fine. This is the first vehicle that I have worked on that has computers. I need to remember to keep things simple. Thanks for all your help.
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