2002 Dakota Sport Plus, 5.9L, AT, quad cab

I recently bought this truck as a project...when I got it, the speedo wasn't working, the ABS and brake lights were on, and the odometer wasn't counting. The guy I bought it from said his mechanic said it needs a new PCM. So, I started researching and learned about the speed sensor on the rear diff and also about the one on the transmission tail shaft. I bought new ones and replaced both, but all the warning lights are still on and the speedo and odometer are still not working.

At this point, I'm beginning to think maybe the guy's mechanic was on to something with the PCM. I just wanted to check here first, though, because I don't know much about these trucks and I don't want to keep throwing unnecessary new parts into it.

Thanks for your help, and let me know if you need any more info.

 

Welcome to the forum.

Is the Check Engine Light on? If so, check for codes, you don't need a scanner. Begin with the key OFF, then turn it to RUN (don't start it), back to OFF, then to RUN, back to OFF, and this time LEAVE IT in RUN. Any codes will display in the odometer window.

The ABS and brakes light indicate a possible problem with the CAB, Controller Anti-Lock brake. It processes the signal from the speed sensors. The PCM itself does not control the brakes.

Check for a blown fuse for the brakes too. There are two. One is in the PDC under the hood, the Power Distribution Center. The other is in the junction box on the side of the dash.

 

Thanks, and thanks for the quick response!

The CEL is on, and I already had the codes pulled: P0500 and P0138. I don't know if I mentioned already, but the truck is 4x4. I read elsewhere that on 4x4s there's an input speed sensor and an output speed sensor, and that one is located on the transfer case. Could that be the problem?

Ok, what can I do to test the CAB? Could the PCM have anything to do with the speedo and odometer not working?

Thanks, I'll look at the fuses when I get home tonight.

 

P0500 is a "no vehicle speed sensor signal."
P0138 is a "1/2 O2 Sensor shorted to voltage" - drivers side, downstream. Don't use Bosch to replace.

You have the 46RE transmission. There is an output speed sensor, you said you changed it, on the overdrive gear case. It doesn't use an input speed sensor - the 45RFE on the 4.7 does.

You'd need a specialized scanner, such as a DRB (dealer) to read the CAB. Most scanners can't read ABS or Body codes.

Do you have 2 or 4 wheel ABS? Look for a wiring harness by the front brakes.

Check the fuses next.

 

Got the sensor (not Bosch...but why, they usually make quality parts I thought?), thanks.

Will I just have to bite the bullet and pay a dealer to check the codes for me, or is there another way to get access to one of those scanners? Places like AutoZone or Advance? Or do they just have regular OBD II?

Haven't had a chance to check these yet, but thanks.

 

Bosch may make quality parts but not for the majority of our Dakota's. Lots and lots of problems, especially with the O2 sensors.

Most places can only scan engine codes, not abs codes. You can certainly try. A good brake shop should be able to read the codes - the dealer for sure.

Check the fuses before you do that.

 

I'd also check the cables running into the cab. I had the same issue minus the engine light. Turns out my abs pump was messed up and the previous owner had just unplugged the cab. So Could be a possibility that the connectors are unplugged or lose. And as stated, fuses would cause this as well.

 

I had a similar problem on a '92 Caravan. It wasn't the PCM, it was the BCM (body control module). It controls a lot of stuff like windshield wipers, gauges, speedo, power door locks, radio--to mention a few. I would surmise the Dakotas have one too. You might have to pay a few bucks, but I'd take it to the dealer and have them diagnose it. No sense shooting in the dark and spending a lot of $ on the wrong parts.
I don't think any codes that are thrown will pin it down for the guys at your local AutoZone or whatever. To find the problem requires going thru a yes/no tree of checks.