Intrepid speed speed sensor problems

[Erehwon]

2000 Dodge Intrepid with 3.2 liter engine. On starting yesterday, speedometer stayed at 0 and transmission, after starting in first gear, went to second at a few mph and locked there. Engine light also came on. Based on searching this group it sounded like speed sensors. Local shop indicated computer showing codes P0700, Transmission circuit failure, and P0731, Ratio Error - Input doesn't match output. Based on that info they replaced both input and output speed sensors and reset the error codes. Got the speedometer working but still goes to second after a few seconds of driving and locks there. Unfortunately, no engine light and no error code (engine light does come on briefly when starting as usual). Sitting idle immediately after starting, I can go to "auto stick" mode and shift back and forth through first, second, and third but still jumps to 2nd after a few seconds of driving. Any ideas where to go next? Car not worth spending substantial $$$.

 

[Bob Shuman]

Yes, it sounds like the transmission output speed sensor was bad. Did you disconnect the fuse to the transmission computer or optionally pull the battery for 5-10 minutes to do a hard reset?

Bob

 

[Erehwon]

I asked the shop the same question and they said it was unnecessary to disconnect the battery since the device they used to read the codes was also capable of resetting the computer. Possible or am I being given a line of .....? I'm fairly sure the battery was never disconnected since the time was still correct and all the radio stations I had entered were still there.

 

[Bob Shuman]

This should be fine if the scan tool actually had that capability for that vehicle, but did they actually remember to perform the reset?

Bob

 

[Erehwon]

Thanks. Engine light finally came back on and shop found input speed sensor connection to transmission control module corroded. Repaired and back to normal. Perhaps that's what killed the speed sensor in the first place.

 

[Bob Shuman]

This does not make sense to me since you indicated the speedometer stopped working when the transmission went into limp mode (2nd gear). This would indicate the output speed sensor (which measures the RPM of the drive shaft to the front wheels) was at fault and not the input sensor (which measures the engine RPM into the transmission).

From your description (originally no speedometer, then had speedometer, but wouldn't shift), I'd suspect that they most likely damaged the input sensor connector when they replaced that sensor. If the facts you conveyed are accurate, then the only other alternative here is that the output sensor failed and then the connector failed too shortly thereafter and before the two sensors were replaced. This seems like a real stretch to me ... they almost certainly caused this poor connection when they removed/reconnected it.

In any event, I'm glad to hear you have resolved the issue.

Bob

 

[Mike Y]

While I agree that actions of the shop probably caused the 'cascade' from one failure to two, I think a lot of times just the fact that ANYONE, no matter how capable, getting in there and disturbing things to look, test, and repair, can cause some secondary failures to come to the surface. I wouldn't be upset with the shop.

Mike

 

[philthy]

if they replaced both i hope they used factory parts
if the pcm stores the code and the trans store the code and were not cleared in both modules then there is a good chance the issue will continue

 

[maxpower]

if they replaced both i hope they used factory parts
if the pcm stores the code and the trans store the code and were not cleared in both modules then there is a good chance the issue will continue

Not true at all, Don't you know what a good trip is? If the check engine lite is on and you fix the problem, depending on what the fault code is for, it will be cleared on 2 or 3 good trips as long as the problem is fixed. A fault code stored WILL NOT make the problem continue (unless the problem is not fixed). The best way to determine if the problem is fixed is by letting the controller make the decision. Doing a battery disconnect or erasing the data on the PCM is not a good idea at all.

Glenn

 

[Bill Putney]

...Doing a battery disconnect or erasing the
data on the PCM is not a good idea at all.

Why not? If the code doesn't come back, then you're good to go. Plus on certain repair jobs, the computer needs to be kicked into a parameter relearn rather than running on the old settings based on defective operation.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

 

[maxpower]

Why not? If the code doesn't come back, then you're good to go. Plus on certain repair jobs, the computer needs to be kicked into a parameter relearn rather than running on the old settings based on defective operation.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

If the transmission is in limp in mode and the speed sensor corrected the problem the PCM will see this. If your gonna clear the codes to see if the problem returns, why not leave the code there to see if the good trip clears it? If a sensor fixed a problem the lite will go out. Why clear out all the monitors and fuel adaptives? If you have a cylinder misfire and replace the plugs/ wires and then clear the misfire monitor you wont know if the problem is fixed until the monitor will run. If you replace a plug wire/plug and don't clear out the monitor the fault code will return when you drive it

Glenn

 

[philthy]

i have seen it happen many times, you wouldn't think it would. but sometimes it does. i have even had to discharge capacitors in modules to get things back to correct