Bad Computer?
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Bad Computer?
I'm working on a 89 ranger 4cyl 5 spd for a friend after another mechanic messed it up. I found out today that it had a computer from a 94 mazda in it. The problem is when it has the 94 mazda computer in it I can enter diagnostic mode and read codes and the fuel pump works like it should but when I put the old 89 ranger computer in it I cant flash codes and the check engine light stays on all the time also when the key is on the fuel pump runs all the time, to me it sounds like the computer. What does eveyone think?
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Joined: Aug 2003
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From: Huntsville, AL
Get the right computer. I had to replace the ecu on my '91 and found out the hard way that theres about 50 different ecu and wiring harness combos for 4.0 rangers between the years of 89 and 93. The computer would plug into the harness but the timing wouldnt advance, the trans would lose overdrive, or some other issue would occur. I tried about 10 different ecus in my truck and all would run the engine but there was always an issue with something not functioning as it should. Long story short, get the right ecu for the truck. Until then you are just shooting in the dark with your troubleshooting.
Logistics Pro
Joined: Jan 2002
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From: suburban atlanta
85, did the other 'mechanic' make any changes to the factory wiring when the 94 ECM was installed? If he did, you'd have to undo those changes before condemning the 89 ECM. This is not a task to undertake without having the wiring diagram available, or another truck for visual comparison. It is also a job that can eat hours without result unless you can determine the current status.
If you can find a good used ECM from a boneyard, it would be a quick way to test, but as the other posts say, it has to be from the correct combination of engine, transmission, 2W or 4W, and Federal or CA emissions.
If you can get access to the shop manual, it has pinouts for every different version offered in that model year.
tom
If you can find a good used ECM from a boneyard, it would be a quick way to test, but as the other posts say, it has to be from the correct combination of engine, transmission, 2W or 4W, and Federal or CA emissions.
If you can get access to the shop manual, it has pinouts for every different version offered in that model year.
tom
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It doesent look like the other mechanic made any changes to the wiring I got my hands on a ecm pinout from a 89 ranger and a 94 mazda and looking at the diagrams most of the wires line up even the diagnostic wires thats why it actually ran with the mazda computer but it threw codes because the mazda has a maf sensor and the ranger doesnt. I checked the wires in the truck versus the 89 ranger diagram and they all match up in the right spot and color code. I dont think the mechanic working on this was smart enough to unpin wires and move them he would of just cut them. I already check the wrecking yards and the only 89 out there that matches the one I'm working on is missing the computer so I got on the cardone website and it looks like there are only two computers the difference is manual and auto trans. I ordered the manual trans computer from autozone for $105 and it should be here by thursday because of the weekend. My oem number cross referenced to the cardone number so it should be the right one.
Logistics Pro
Joined: Jan 2002
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From: suburban atlanta
Sounds like you are doing a lot more than the original mechanic. I don't know Cardone rules on the core, but it couldn't hurt to look inside. The ECM supplies ground to the fuel pump via a transistor. I'd bet the transistor is shorted, supplying ground all the time.
Probably not worth a whole lot of time investigating.
tom
Probably not worth a whole lot of time investigating.
tom
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Post Fiend
Joined: Oct 2005
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From: Kiev, Ukraine
Gentelmen!!! '94 PCM do not fit '89 Ranger.... Why!!??? First of all, different wiring harness, other sensors (for exmple '86-91 EEC-IV had MAP+IAT to calculate air mass, '94 has MAF sensor), '89 is 2 digit DTC codes, '94 - 3digit, '89 works with distributor, '94 - with coil pack!!!
do you really want to change wiring? Just use right PCM!
do you really want to change wiring? Just use right PCM!
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Gentelmen!!! '94 PCM do not fit '89 Ranger.... Why!!??? First of all, different wiring harness, other sensors (for exmple '86-91 EEC-IV had MAP+IAT to calculate air mass, '94 has MAF sensor), '89 is 2 digit DTC codes, '94 - 3digit, '89 works with distributor, '94 - with coil pack!!!
do you really want to change wiring? Just use right PCM!
do you really want to change wiring? Just use right PCM!
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Sounds like you are doing a lot more than the original mechanic. I don't know Cardone rules on the core, but it couldn't hurt to look inside. The ECM supplies ground to the fuel pump via a transistor. I'd bet the transistor is shorted, supplying ground all the time.
Probably not worth a whole lot of time investigating.
tom
Probably not worth a whole lot of time investigating.
tom
Post Fiend
Joined: Oct 2005
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From: Kiev, Ukraine
yeah, I understand, usually all actuators (including fuel pump relay) are controlled with 986T04. As I remember, FP relay pin is #22, so, about switch location, look at connector, U see sticker and it is up side up (LOL) right wall of EMC, the firts transistor near the connector (ECM wall is used like a cooler). Try to change it. remove clip and desolder it carefully (ore ask a pro), solder new one and try againe. Here this switch is about $1-3!! But you must solder like a pro to get no board damage. Use soldering gel.
Anyway pull codes. Sometimes reading PIP wrong PCM turns FP on. Getting trouble codes I can understand what's wrong. Clear all codes and post here current fault only
Anyway pull codes. Sometimes reading PIP wrong PCM turns FP on. Getting trouble codes I can understand what's wrong. Clear all codes and post here current fault only
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Since I already ordered the new computer I'm going to try it first, I might try to fix the old computer later. I've sodered on computer boards before(fixing gauges and tachs) but I never did like doing it. Thanks for the info about the fuel pump transistor. Also I cant pull codes the check engine light just comes on when the key is on and truck started. When I jump the connections nothing happens, no diagnostic mode at all in koeo or koer. I checked and the light is not shorted to ground.
Post Fiend
Joined: Oct 2005
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From: Kiev, Ukraine
Since I already ordered the new computer I'm going to try it first, I might try to fix the old computer later. I've sodered on computer boards before(fixing gauges and tachs) but I never did like doing it. Thanks for the info about the fuel pump transistor. Also I cant pull codes the check engine light just comes on when the key is on and truck started. When I jump the connections nothing happens, no diagnostic mode at all in koeo or koer. I checked and the light is not shorted to ground.
http://fordfuelinjection.com/?p=6
Look at diagram and you will undestand.
Post Fiend
Joined: Oct 2005
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From: Kiev, Ukraine
all actuators are negative wire controlled.
CEL and FP relay are negative wire controlled too, may be connector is OK and you have 2 short transistors. When EEC relay actuates, all actuators are supplied with 12V. So if transistors are short CEL is on and FP relay is on!
CEL and FP relay are negative wire controlled too, may be connector is OK and you have 2 short transistors. When EEC relay actuates, all actuators are supplied with 12V. So if transistors are short CEL is on and FP relay is on!
