strange transmission check engine light issue
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strange transmission check engine light issue
I have a 1994 ford F150 with automatic transmission. Driven every day in warm weather it just takes a manual downshift on a hill and the transmission shifts firm. After sitting a week when cold the transmission will not shift up from first gear it will only shift manually up to 2nd. not 3rd. The check engine light will go off while the truck is not shifting right while cold. It stays on when the engine and transmission warm up. The only other issue I notice is the A/C doors inside the heater case will switch to the floor on a long hill. I drove the truck today in cold weather and the check engine light will keep going on and off and it will shift in to 3rd gear when warm but the problem never really go's away. So the problem is really made worse by outside temperatures. The A/C problem makes me think there is a vacuum leak. I had a transmission years ago before check engine lights I changed the vacuum modulator and found no vacuum leaks on that one and that didn't fix the problem. I made the mistake of putting fresh fluid and a new filter min that one and the transmission died on that car. any ideas out there. 
Last edited by old german; Dec 27, 2016 at 08:17 PM. Reason: fix errors
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update to strange transmission problem
I got some time yesterday and ran a KOEO test. The self test yeilded a fault code of 123 (Throttle Position Sensor above maximum voltage).
The continuous stored codes are 121 123 124 334. The first three all lead to a TPS sensor. I am going out with a voltmeter and doing a resistance test ASAP. I will keep this post updated.
Is it possible this one sensor can cause such a huge drivability issue.
When I purchased this truck from a local dealer for a very reasonable price. They were very insistent on knowing when I was coming for a test drive. When I arrived the truck was sitting in front of the dealership running? I drove the truck nearly every day last summer. after a few weeks CEL lights up, Only problem just a lack of downshift on steep hills just did it manually no big deal. Fall came along I let it set for a week BOOM! Drive it every day drives ok. I think they knew what was up. If replacing the TPS fixes this thing I will be amazed.
The continuous stored codes are 121 123 124 334. The first three all lead to a TPS sensor. I am going out with a voltmeter and doing a resistance test ASAP. I will keep this post updated.
Is it possible this one sensor can cause such a huge drivability issue.
When I purchased this truck from a local dealer for a very reasonable price. They were very insistent on knowing when I was coming for a test drive. When I arrived the truck was sitting in front of the dealership running? I drove the truck nearly every day last summer. after a few weeks CEL lights up, Only problem just a lack of downshift on steep hills just did it manually no big deal. Fall came along I let it set for a week BOOM! Drive it every day drives ok. I think they knew what was up. If replacing the TPS fixes this thing I will be amazed.
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much better
It was getting late, but i put the new TPS in the throttle body it Has a 302 so I had to partially remove the throttle body, put the new TPS and a vacuum hose that fell apart when I pulled it off. reassembled things.
The motor started right up and it idled fast after a few seconds of warm up it returned to normal.I put some tools away and took it for a short drive. No CEL,shifts as it is suposed to no slippage and downshifts when you push down on the gas. will need to run a KOEO test to see if the all clear code of 111 will show up. Thanks Mark.
The motor started right up and it idled fast after a few seconds of warm up it returned to normal.I put some tools away and took it for a short drive. No CEL,shifts as it is suposed to no slippage and downshifts when you push down on the gas. will need to run a KOEO test to see if the all clear code of 111 will show up. Thanks Mark.
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From: Ideeho
Glad you found the issue....I hate computer controlled stuff for this very reason.......the reason the TPS sensor affected the transmission is because the trans computer needs to know where the throttle is at.......If they can't "talk" to each other ........one of them refuses to do their job properly.........it's as bad as working in corporate America LOL
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