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Discussion Starter · #1 ·
I have a 98 Dodge Ram 1500 5.2 (318) that keeps getting P0720 code (check engine light). The symptom first was truck felt like it was taking off in 2nd or 3 rd gear, If you manually down shifted to 1st it would take off, then you shift to drive and it would shift ok. I have spent $900 on supposly getting fixed. They have replaced all sensors on inside transmission, speed sensor on outside transmission. Transmission shop tried several thing, with no luck. They finally replaced the rear oxygen sensor after the catalyst converter. It fixed it for 3 weeks. I now encountered problem again when I came to a full stop, tried taking off, but it felt like it was in 3rd or overdrive. It finally got going and seems to be ok, except it takes a little longer to shift from 1st to 2nd gear. Check engine light on. I found out there are 2 oxygen sensors, maybe other one needs to be replaced. Supposly the oxygen sensor was grounding out and it was on same circuit as speed sensor. I also read there is a speed sensor at differential. Has anyone experienced something like this???
 

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output speed sensor

I think there is an output speed sensor in the side of the transmission case that could be your problem. Maybe take the sensor out and see if there is a buildup or something on the part that the sensor is reading. This happens with abs sensors in front hub bearings, they get built up with rust or debris and the sensor will not read.
 

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Thanks Brian for the reply, I will verify they have replaced that sensor on the tickets I have. I have a feeling they may have checked either voltage or continuity on it. Supposely all sensors inside the transmission (by dropping the trans. pan) has replaced as well as the wiring harness has been replaced.
 

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I have had the same problem, I changed the sensor on the tranny (outside) worked for a couple of weeks. Light came on again. I changed the "speed sensor" on the rear diff. Has been working fine now for 3 weeks.
 

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i had the sensor on the axle go out, and it triggered the ABS light but no engine codes, and affected the speedometer. had it replaced two years ago. now i have the p0720 code, but no worries from the ABS. I'm aiming at the speed sensor in the tranny. I'll let you know.
 
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