When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey guys, My 96 has about 265k miles on it and no mods that I know of. My check engine light will come on and the RPMs will drop down to idle. I will have to lift off the throttle and press it down again to get the engine to wake back up. Also once this has happened the trans will start shifting funny. It will shift through the gears quickly to high gear even at low speeds and bog the engine down. Sometimes these shifts can be very hard too. After a while the trans will go back to normal. The problem happens more when the engine isn't warmed up good but does do it at all times. It's been doing this maybe every other day but this morning it did it like 5 or 6 time on my way to work so I turned around and came home. Don't want to be stuck in downtown Houston with a dead truck. One more thing, put the scanner on it to try and see if it threw a code and none where found. Any suggestions?
Get it scanned for codes, that's the best way to pinpoint the trouble. That being said I would check the Rear Antilock Brake sensor (RABS) on the top of the rear axle may cause the weirdness you're experiencing, possibly the Throttle Position Sensor (TPS) but those are just guesses.
Remove the RABS and clean the crud off it, check the wire socket and pins for corrosion ect. re-install it and see what happens.
Take it to Autozone...sometimes they can scan our diesels. It depends on the guy using it. Some Actrons will work.
Each scanner maker is different. You need to ask if they are capable of scanning our diesels. Some are...some aren't.
IMO, The trouble you are are having isn't OBD specific, I believe it's the RABS, it cannot be detected through the OBD port. It sends a signal to the Programmable Speedometer Odometer Module (PSOM) that inturn sends a signal to the PCM that inturn sends signals to the tranny telling it when to shift. The RABS is magnetic and will accumulate fine metal shavings greatly reducing the signal output. If you clean the "fuzz" off of it and ake it work again.
When the RABS is bad the OD light on the shifter will usually blink, the tranny shifts hard.
Ok, I thought about replacing the TPS because I found one for 35$. Come to find out I'm looking at the "Pedal" position sensor and thats why the parts dont look the same. DOH. I've looked all over the engine and can't find a TPS,
not to say its not there, just I dont know where to find it.(maybe it's not there, maybe it doesn't have one, only The Shadow knows) Anyway, I'm going to get a "PPS" and clean the RABS and hope that cures the problem. If it has one, should I replace the TPS also?
Ok, I thought about replacing the TPS because I found one for 35$. Come to find out I'm looking at the "Pedal" position sensor and thats why the parts dont look the same. DOH. I've looked all over the engine and can't find a TPS,
not to say its not there, just I dont know where to find it.(maybe it's not there, maybe it doesn't have one, only The Shadow knows) Anyway, I'm going to get a "PPS" and clean the RABS and hope that cures the problem. If it has one, should I replace the TPS also?
TPS is on the pedal ...
Never heard of it causing the trans to go into limp though...
I am probably wrong but if there was a short somewhere would or could this happen,the other week I had my batteries unhooked and when I hooked them back up my truck also shifted this way.
Also I had a 91 f250 gasser that did what you are explaining and it ended up being the starter sounds silly but it was shorting out the truck it was almost like someone had flicked a switch or unhooked the batteries.
I am probably wrong but if there was a short somewhere would or could this happen,the other week I had my batteries unhooked and when I hooked them back up my truck also shifted this way.
Also I had a 91 f250 gasser that did what you are explaining and it ended up being the starter sounds silly but it was shorting out the truck it was almost like someone had flicked a switch or unhooked the batteries.