2003 Rubicon Speedsensor/speedometer issue - JeepForum.com
 
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post #1 of 4 Old 09-21-2017, 08:38 PM Thread Starter
descent03
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2003 TJ Wrangler 
 
Join Date: Jun 2013
Location: temecula
Posts: 11
2003 Rubicon Speedsensor/speedometer issue

Hey guys,

Recently got the p0500 speed sensor CEL along with a speedometer that doesn't work, just sits at 0mph and never moves.

Tried so far

Replaced the speed sensor - speedometer still doesn't function
removed the cluster and cleaned the connection and tested for loose pins - speedometer still doesn't function
ran the self diagnostic on the cluster and the speedometer does run through the diagnostics along with all other cluster lights and functions.
all fused are fine

Only issue I am having is the speedometer, the tac and all other gauges work (not sure about the odometer, will need to check that out)

Can anyone run me through how to test the connection from the PCM to the cluster and from the sensor to the PCM. I am not a novice for DIY but anything with electrical systems makes me nervous.

Not sure if it is related but I have also been having issues recently with the radio randomly kicking off, speakers and head unit. I suspect that is a bad harness and will be taking a look at that tomorrow but not sure if I should consider them related.

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post #2 of 4 Old 09-22-2017, 06:59 AM
NotURMailman
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DISCLAIMER:
I wrote this up using a 2005 TJ FSM and am assuming there were no changes in this system between 2003 and 2005.

I am telling you what I would do to test the wiring, no guarantees here.

Dig into your electrical and vehicle control systems at your own risk.

Unless you are testing for power I strongly recommend you do all circuit testing with the battery disconnected.

On the black 38 way PCM plug C1:
pin 18 has an 18 gauge bark blue wire with an orange stripe that is the signal wire from the sensor.

On the speed sensor plug:
pin 1 is a 20 gauge yellow wire with a pink stripe that is the 5 volt supply from the PCM
pin 2 is a 20 gauge dark blue wire with a dark green stripe that is the sensor ground
pin 3 is an 18 gauge bark blue wire with an orange stripe that sends the signal to the PCM

1 - put something on your accelerator pedal to open the throttle (just ensure that it is not closed as if at idle)

2 - turn the key on, disconnect the plug from the speed sensor and verify 5V supply on pin 1
If no 5V supply, you have found the problem and you need to figure out why and fix it.
If 5V is present, proceed to next step.

3 - turn key of and disconnect battery

4 - verify continuity between VSS plug pin 2 and ground
If there is no continuity to ground you have found the problem and need to pin point and fix it.
If the ground is good (near 0 ohms), proceed to next step.

5 - disconnect black plug from PCM C1 plug and verify continuity between sensor pin 3 and PCM pin 18.
If there is no continuity you have found the problem and need to pin point and fix it.
If the connection is good (near 0 ohms) open a cold beer and make an appointment at the dealership for diagnostics.

FYI
- the sensor signal circuit has splice (S129) at the rear of the engine that will have multiple (up to 7 depending on vehicle configuration) 20 gauge yellow with pink stripe wires connected together
- the sensor ground for the sensor is provided though a low noise sensor return circuit in the PCM, so if you have loss of sensor ground check and clean all PCM grounds and hope it's not a bad PCM

NOTE:
If you do have a loss of ground to the sensor, diagnosis may be difficult.
The FSM sates in multiple location that "For proper diagnosis of the vehicle speed sensor, the PCM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the odometer/trip odometer, a DRBIIIt scan tool is required.

Good luck and let us know what you come up with!


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post #3 of 4 Old 09-22-2017, 11:57 PM Thread Starter
descent03
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2003 TJ Wrangler 
 
Join Date: Jun 2013
Location: temecula
Posts: 11
Just a quick follow up question:

Thanks for the write up, I have 5v and ground but I am confused about the c1 pin 18 test. Isn't that to the cam position sensor and not the speed sensor? I have not looked at a wiring diagram so I guess they could be on the same circuit but I figured I would ask.

Ironically enough, when I took a closer look at that wire/pin I noticed it has been repaired before (previous owner I assume) and a shoddy job at that. Either way I am going to re-pin and do a proper solder/heat wrap the wire.
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post #4 of 4 Old 09-23-2017, 12:01 AM Thread Starter
descent03
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2003 TJ Wrangler 
 
Join Date: Jun 2013
Location: temecula
Posts: 11
ah, the 03 Rubicon has 32 way pcm connectors and not a 38 way.
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