Check Engine light, RPM rise, loss of fuel economy
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Check Engine light, RPM rise, loss of fuel economy
EDIT: Mistakenly posted this in the 2nd gen forum. I have a 1998 5.2 4x4.
So I had to travel from Detroit, Michigan to Waterloo, Canada for a week of training, and on the way here the Check Engine light came on and the RPMs suddenly jumped past 3k at highway speeds. A quick scan of the gauges showed nothing amiss, but the fuel economy was 12mpg down from 18mpg (obviously because of the RPM climb). I'm guessing overdrive was disabled thus the RPM increase, but I'm not sure exactly what happened. Is this the limp mode I've read about? So I made it to the hotel and pulled out the trusty scan tool (you all keep one in your truck right?). The codes I'm getting are p0123 and p121f, basically relating to throttle position sensor. I'm sure this sensor is readily accessible assuming off the throttle body if I can source parts. I'm not exactly setup for auto repair since it's the middle of winter and I'm in a hotel. Thoughts? Best aftermarket TPS?
Thanks,
Jared
So I had to travel from Detroit, Michigan to Waterloo, Canada for a week of training, and on the way here the Check Engine light came on and the RPMs suddenly jumped past 3k at highway speeds. A quick scan of the gauges showed nothing amiss, but the fuel economy was 12mpg down from 18mpg (obviously because of the RPM climb). I'm guessing overdrive was disabled thus the RPM increase, but I'm not sure exactly what happened. Is this the limp mode I've read about? So I made it to the hotel and pulled out the trusty scan tool (you all keep one in your truck right?). The codes I'm getting are p0123 and p121f, basically relating to throttle position sensor. I'm sure this sensor is readily accessible assuming off the throttle body if I can source parts. I'm not exactly setup for auto repair since it's the middle of winter and I'm in a hotel. Thoughts? Best aftermarket TPS?
Thanks,
Jared
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Joined: Jun 2005
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From: Riverton, UT
P0123 Throttle Pos Sens Voltage Hi
P0121 TPS Voltage Does Not Agree with MAP
I have no idea what a p121f is. There is no such codes for our trucks so I included a P0121. Both of these are a Throttle Body Position Sensor code (TPS). You need to replace the TPS sensor then reset the PCM: https://dodgeforum.com/forum/1st-gen...ine-light.html
While you have it out you might think about cleaning the Throttle Body and IAC: https://dodgeforum.com/forum/1st-gen...ttle-body.html If you do clean the TB then reset the PCM again.
Most likey what has happened is the readout from the sensor is open too far so the transmission wont engage into Overdrive. Limp mode is when the transmission is stuck in 3rd gear ONLY. Even when you start out you will be in 3rd gear.
P0121 TPS Voltage Does Not Agree with MAP
I have no idea what a p121f is. There is no such codes for our trucks so I included a P0121. Both of these are a Throttle Body Position Sensor code (TPS). You need to replace the TPS sensor then reset the PCM: https://dodgeforum.com/forum/1st-gen...ine-light.html
While you have it out you might think about cleaning the Throttle Body and IAC: https://dodgeforum.com/forum/1st-gen...ttle-body.html If you do clean the TB then reset the PCM again.
Most likey what has happened is the readout from the sensor is open too far so the transmission wont engage into Overdrive. Limp mode is when the transmission is stuck in 3rd gear ONLY. Even when you start out you will be in 3rd gear.
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I was able to find a parts store and got a TPS for $50. Install was luckily fast since it's 5 degrees F, and I swapped it in a hotel parking lot. Initially idle RPM was 1500 or so. Used scan tool to reset base voltage and all is well.
Thanks,
Jared
Thanks,
Jared
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Joined: Jun 2005
Posts: 14,228
Likes: 19
From: Riverton, UT
And another one bites the dust.
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Joined: Jan 2013
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From: Southern Deserts of California
Hello hydrashocker i must say you are the man! this thread is a few years old but if anyone's still around my 98 durango 5.9L has just thrown the same code P0121 TPS Voltage Does Not Agree with MAP. I have replaced TPS then disconnected my battery for about 30 min now this should reset the pcm righ? My problem wasn't solved. 
(my truck at random would have a rough idle (replaced cables plugs cap rotor AIS ICV) the big problem is randomly like 1day maybe a week ill have my truck loose all power and as i press the gas the rpms rise and drop quickly and just last week i finally got P0121 (finally something to go off of) but ive fixed it and still having problems. Ive taken it to crystler (before i got the code) and they told me theres nothing wrong with it.(they prob just trying to get me to buy a new truck) Im wondering if there might be something wrong with a circuit ? anything will help please thanks guys
(my truck at random would have a rough idle (replaced cables plugs cap rotor AIS ICV) the big problem is randomly like 1day maybe a week ill have my truck loose all power and as i press the gas the rpms rise and drop quickly and just last week i finally got P0121 (finally something to go off of) but ive fixed it and still having problems. Ive taken it to crystler (before i got the code) and they told me theres nothing wrong with it.(they prob just trying to get me to buy a new truck) Im wondering if there might be something wrong with a circuit ? anything will help please thanks guys
Last edited by Joseph Taylor; Jan 28, 2013 at 02:17 PM.