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07-24-2008
Speedometer is not working. I changed the VSS. Still Nothing. My SES light is on and the codes that came up were PO502 and PO503, they are both speedometer codes. I checked the plug at the VSS with a test light and it did not light up the bulb. All fuses in the car are good. I am curious if I need to check the plug in with a MULTIMETER if it is low voltage? Any help would be appreciated. I really do not want to take it to the shop and get raped for diagnosing the problem.
07-24-2008
502 vehicle speed sensor A circuit low input
503 vehicle speed sensor A erratic/high
looks like the speed sensor is no good, i dunno there are the codes for you hope that hepls
07-24-2008
Here's the GM diagnostics for p0502, P0503 is basically the same. It sounds like you have a wire problem somewhere. Is this code on all the time? Does it come right back on when it's cleared? I would check the engine bay and under the vehicle for any broken/chaffed/suspicious looking wires. Let us know what you find.
I take it you have access to a multi meter and a jack? Then follow the steps and if the answer to the step is yes follow the y- to the corresponding step if its no follow the n-. The number of the step is above it. Good luck.
Place transmission in Neutral or a drive gear (must not be in Park).
Turn the ignition switch to the OFF position.
Disconnect PCM connector C1.
Connect a digital multimeter (DMM) to terminals 64 and 65 of the PCM connector C1.
Select AC volts on the DMM.
Rotate the Right drive wheel manually and rapidly, and observe the DMM.
Is the measured voltage greater than the specified value?
0.4 V
y- Go to Step 13
n- Go to Step 4
4
Select ohms on the DMM.
Is the resistance between terminals 64 and 65 greater than the specified value?
1,864 ohms
y-Go to Step 5
n- Go to Step 6
5
Inspect circuits 400 and 401 for an open.
Repair the circuits if necessary.
Refer to General Electrical Diagnosis in Wiring Systems.
Was a condition found?
--
y Go to Step 14
n Go to Step 10
6
Does the DMM display a value less than the resistance specified?
981 ohms
y Go to Step 7
n Go to Step 8
7
Inspect circuits 400 and 401 for a short together.
Refer to General Electrical Diagnosis in Wiring Systems.
Was a condition found?
--
y Go to Step 14
n Go to Step 10
8
Connect one lead of the DMM to a good ground.
Connect the other lead to terminal 64, then terminal 65.
Is either resistance lower than the specified value?
50 K ohms
y Go to Step 9
n Go to Step 11
9
Inspect circuits 400 and 401 for a short to ground.
Refer to General Electrical Diagnosis in Wiring Systems.
Was a condition found?
--
y Go to Step 14
n Go to Step 10
10
Disconnect the VSS and connect a DMM from terminal A to terminal B of the VSS.
Is the measured resistance within the specified range?
981-1,864 ohms
y Go to Step 11
n Go to Step 12
11
Remove the VSS and inspect the sensor rotor on the final drive carrier assembly for damage, looseness or misalignment.
Refer to Unit Repair.
Was a condition found and corrected?
--
n Go to Diagnostic Aids
12
Replace the vehicle speed sensor.
Refer to Vehicle Speed Sensor Replacement .
Is the replacement complete?
--
--
13
Replace the PCM.
Refer to Powertrain Control Module Replacement/Programming in Engine Controls.
Is the replacement complete?
--
--
14
Repair the wiring as needed.
Refer to Wiring Repairs in Wiring Systems.
Is the repair complete?
07-26-2008
I just saw your PM, sorry we have been out of town the past few days and have had limited internet access time. The above testing info is a great start to see what you have. Not sure about the light bulb test? The speed sensor puts out an AC voltage that goes up as wheel speed increases but it is a very very low voltage. Follow the steps above and post back what you come up with but as mentioned above it is likely a wiring problem. You can also remove the speed sensor via one 10mm head bolt that holds it in which is accessable above the far right/passanger side of the trans where the passanger side axle goes in. If you pull the speed sensor out look at the end that goes into the trans and see if you have any large pieces of metal on it. You will likely find some dark gray paste like stuff on the sensor which is normal, its a magnet and will pick this up over time. Also with the trans in PARK see if you can put a screwdriver againts the reluctor wheel teeth - ring used for speed sensor - and try to pry it forward and backwards, it should be solid and not have any movement other than the slop in the park gear. Check the connector and speed sensor good for corrosion and ohm test the sensor without being hooked up and see what it checks out. If it is fine at the sensor but not at the connector then you have a wiring problem. ALSO..... something I found out the hard way a few years back diag'n an ABS problem on a GTP.... You may have AC voltage that will read like it is supposed if one of the wires is broken! Trying fishing out that problem when you think it checks ok but really it doesnt! That ended up being a bad wheel speed sensor harness and took a long time to trace out. Just use caution and test test test!
07-29-2008
Alright I need the wiring diagram, I know one of you has it. Where is the pcm connector C1 located?
07-29-2008
Can I just run new wires from the connector to the speed sensor?
07-29-2008
You have to be able to get your PCM there should be 2 long connectors screwed into it. and as far as running a new wire no you cant really because the wires are a certain resistance and messing with it too much may fubar something. A wire repair or maybe even replacement of a small section is usually all it can take. And let me see if I can find a schematic....
07-29-2008
3100 or 3800?
07-29-2008
PCM connector C1 is the blue connector of the two. After you disconnect it look inside of it and you should see two squares/rectangles that are small and either above or below the terminals depending on how you look at them. Make it so the squares are above the terminals, look at it this way. The terminals then go from 1 to 40, starting on the bottom row going left to right. The upper row is 41 to 80, just count over till you have the appropriate terminal to test.
07-30-2008
IT is the 3.8 SC? where is the ecm on these cars?
08-01-2008
Found the break in the wire!! When the front hydraulic mount went it must have broke it. Anyways I am good to go. The car shifts like perfect.
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