Hey all. Newly purchased a very nice 97 Dakota extended cab. 5.2 318 V8 - 2WD. Love the truck. New when I bought it it had a few quirks since it had (yes I know it’s a risk) been flooded up to over the wheel hubs. No water damage to the PDC or the PCM or instrument panel. Runs great but throws voltage high codes on the Downstream 02 sensor and the tranny heat sensor. The O/D and trans temp lights come on for a brief moment about 5-10 mins after I start her up. They chime and go off. The engine light doesn’t come on but the codes hold. PO138,713,141,711. I pulled these from OBD test results on multiple occasions. I raised her up the other day and swapped out front and rear shocks and I used air tools. When I sat her back down and took her for a test drive her speedometer and tach were no longer functioning. Which leads me halfway to the speed-sensor on the rear differential. I have two main questions aside of any advice or if anyone has experienced this combo before.
1. Do the downstream O2 sensor, tranny heat sensor, speed sensor and or input sensor on the back of the tranny case all lead back to a common grounding point? It seams everything leads back to S101, S103 from the VSS and PCM and G200 for the O/D switch itself and G101/S170 for the veh speed control servo. (I had an issue with a faulty ground on the rear right turn and reverse lights which I fixed independently already but they led back into S101 and on to G101 as well so at this point I’m pretty sure I have a main grounding point issue somewhere.???..)

2. Can anyone actually answer as to if the Tach and Speedo are both fed info from the speed sensor? I can’t seem to find a straight answer to this anywhere. I cannot believe they both would fail at the same time but 🤷🏻‍♂️..

So I’ve answered any potential questions about the cruise control. The light comes on when you initiate the cruise system but it does not set or accel or respond in anyway. Also while cruise is on the O/D light comes on and off. Though I feel no change to the engines performance when this is happening.

The horn fuses/ relays all test fine but I only have high horn tone.

I have pulled and cleaned the O2 and Heat sensor connectors and die greased them. I also ohm tested all connections and from what I can see they are testing properly (but I am not an electrician by any means). Readings on the multimeters flux from like .03-.457 ohms on the O2 and tranny heat sensors.

I have checked all fuses and relays in the entire truck and all test for continuity and I find nothing burned or out of the ordinary. (Again not an electrician). I am raising her up to test the speed sensor and it’s connections today but it’s my hope it tests bad and just needs replaced. Over all I find it too coincidental that all sensors would be bad at the same time and that the tach and Speedo would drop out at the same time as well; but she is 24 years old and I’m just getting acquainted with owning a dodge and their quirks. Love this truck to death though..

History as I know it...
- Truck is originally from Arizona.
- Was flooded over hubs in Arizona sometime prior to 17”.
- Bought at auction and titled to ohio in 17”.
- Had a “full” engine check and tuning at like 209k by the garage that purchased and retitled retitled her. - Bought in 17” and titled and inspected in PA. Used since then to haul a boat during season was not a regular daily driver.
- I purchased in nov 21 with 221441k on her.
- Body and frame are scary clean for her age and she has all the original interior which verifies the water level not coming more than two inches into the carpets from under the doors.

Since I purchased her:
- Rewired both of the grounds for the right rear reverse light and turn signals. (These I short ground to the chassis under the taillight mounts.) I know it’s quick and dirty 😂
- new front and rear shocks
- removed the high intensity LED headlights that were installed at some point and removed and replaced the 30amp mini fuses with the specked 15amp mini they should have had. I am assuming the new bulbs were popping the fuses so they stepped them up to “twice” the factory spec..(wtf really...smh) and I am afraid that this may have at the least aggravated some of the electrical issues if not caused an few but again... not an electrician.
- new power steering pump
- oil change to Schaefer’s 5w-30 with recommended Mopar filter
- replacement of interior bulbs and rear tail and turn and parking bulbs.

hope this has been as concise as possible...

Any advice and clarification would be fantastic.

 

Welcome to DF!

Speedo is fed from the VSS on the tailhousing of the trans. Tach is fed by the PCM itself.

Check the wiring for the rear O2 sensor. There is a 12 volt heater circuit, and a 5 volt sensor circuit. If you have a scanner that can read live data, see what the voltages look like at idle. Might just be a short in the sensor. (common, especially on high mileage trucks.)

Moving this to the 2nd Gen Dak section for ya. Welcome to DF!

 

Thank you for the clarification and proper location placement. I will take a look and see. I don’t have a live data scanner unfortunately but I may know someone who does. 👍🏻