Code P0502 and P0503

**40th GP** · 07-03-2014

Hey all:

Was driving along and car started bucking and speedo jumping all around. Then speedo completely died and car started running fine. Has codes P0502 and P0503 pending. I suspect the P0503 was when things were bouncing around going wonky, then the P0502 came when it totally cut off.

Any ideas on what to check first? Is it possible to test the speed sensor, and is it the sensor on the trans? What would make it go out slowly (giving the P0503), don't they usually just die completely? Does it sound more like a wiring issue?

**BillBoost37** · 07-03-2014

It would be a huge help if you'd tell us what 502 and 503 stood for.

**40th GP** · 07-03-2014

Ooops, sorry. P0502 is Vehicle speed sensor A circuit low input, and P0503 is Vehicle speed sensor A circuit intermittent.

**BillBoost37** · 07-03-2014

I'd start off with checking the wiring that goes to the differential cover on the passenger side right behind the ps pump. That's the vehicle speed sensor. Irf that doesn't do it.. there's a 10mm stud holding the sensor to the cover. Usually the wiring has a plastic clip that holds it to the stud though. I say this..because it's very tough to see in there.

**40th GP** · 07-03-2014

I will take a peek when I get home. The way it was acting wonky for a bit then cut out I was thinking wiring as well. It seems like the sensor it self would either work or not work, no?

**40th GP** · 07-23-2014

Tested the sensor and was not getting any reading, so I replaced it. It was very tough to get in there and I am not sure if I had a good connection, but that did not solve the problem. Still getting code P0502 -- speed sensor circuit A low voltage.

I tried clearing the code while driving, and everything went wonky. It must have been compensating for not having the signal, and I disrupted it. Pulled over and restarted and it ran fine again, but still no speedo and still has the code. the speedometer does flicker to life every so often for a split second.

I still suspect the wiring due to the slight fluctuation of the speedo needle every now and then, but things are very tight in there and I can't really get a good test. And am I just checking the resistance of the wires?
What should I proceed to check from here?

**BillBoost37** · 07-24-2014

Originally Posted by 40th GP

Tested the sensor and was not getting any reading, so I replaced it. It was very tough to get in there and I am not sure if I had a good connection, but that did not solve the problem.

I'm a bit confused from your post. You say a new sensor fixed the problem, then say it didn't.

I'd ask you to make up your mind, but the rest of your post mentions it's still not fixed.

I'd start by looking over the wiring in the area. See if it shows any signs of being yanked etc.

**40th GP** · 07-24-2014

I don't see anywhere that I said it fixed the problem, but to be fully clear it did NOT fix the problem. Maybe too much junk dropped in my eyes while I was under the car

Every once in a while the speedometer will jump to life for a fraction of a second or so, then dead again. I did look at the wiring and the wires are bent where it enters the connector, but I didn't see any broken wires. I will take it apart for closer inspection, but there is not much slack in those wires so there is not much to work with there. Assuming those check out do I just follow the wires up and keep checking along?

**40th GP** · 08-22-2014

I have not been able to spend much time on this and it is still not working. Does anyone have a wiring schematic or diagram for this circuit?

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