Speedometer problems

[TheJake]

Hi,

Looking for some help to solve a small problem with my 2001 Sequoia. I recently pressure washed my engine and the next day I notice that my speedometer was kind of jerky as it moved. It would hang for a split second and then jump up a couple of times until I reached cruising speed. This went on for a couple of weeks and then it started to just hang up around 45 – 50 mph and not go any further and I also noticed that it was hanging on the way down too. Now it is just hanging around 15 - 20 mph. I check the speed sensor connection at the tranny and everything looked dry inside the rubber boot. I am not sure where the wires go from there, but I would like to check any other connection points before I take it in for service to see if any water got somewhere is should not have. Anyone have a wiring diagram they would like to share?

EDIT:

If the speed sensor at the tranny is at fault, should that create other problems? I thought that the speed info is sent to the master control unit for other components to function correctly. If I pop in a new speed sensor is there anything I should be aware of before hand, or is it a simple remove and install operation?

Thanks,
Todd

[TheJake]

Anyone have any ideals on what might be causing the problem? It seems to run OK, but I don't know if a problem like this should show any other symptoms or not???

Thanks,
Todd

[diablito1975]

is your odometer still recording miles when driving?

[TheJake]

Yes, the odometer and both trip-meters are still working correctly as far as I can tell, I haven’t compared them with a GPS but they seem accurate compared to highway mileage markers.

Thanks,
Todd

[diablito1975]

you could try getting a used speed sensor from a wrecked sequoia or tundra, installation is very simple just remove the old one and pt the new one, that way you dont have to spend all that money on a new one and find ot that is not the problem

[tinik]

Originally Posted by TheJake

Yes, the odometer and both trip-meters are still working correctly as far as I can tell, I haven’t compared them with a GPS but they seem accurate compared to highway mileage markers.

Thanks,
Todd

if your odo is functioning properly, then you have a problem with your speedometer not a sensor.

[TheJake]

Originally Posted by tinik

if your odo is functioning properly, then you have a problem with your speedometer not a sensor.

I only question this solution because:

1. I know very little about how this system is designed.
2. It seems very coincidental too have occurred just after I pressure washed the engine.
Is there a junction/connection coupling between the speed sensor and the speedometer that could have gotten wet/damaged during the pressure washing of the engine compartment? I only know that there are three (3) wires connected to the sensor and they disappear into the wiring harness maze shortly after that.

It is odd that the speedo still moves up OK for the first 10 or 15 mph like it should, but then it starts to stutter and hangs around 30 - 35 mph, and it always starts to drop back down when slowing down below where it is stuck and always returns to 0 mph when stopped.
Maybe it is the speedo and it got shorted out because of something getting wet somewhere else… like I wrote, I Know very little about the system, just trying to get as much info before I start tearing apart things.

Thanks for all of your help,
Todd

[RogueRider]

The No. 1 vehicle speed sensor outputs a 4−pulse signal for every revolution of the rotor shaft, which is rotated by the transmission output shaft via the driven gear. After this signal is converted into a more precise rectangular wavefrom by the waveform shaping circuit inside the combination meter, it is then transmitted to the ECM. The ECM determines the vehicle speed based on the frequency of these pulse signals. If the ECM does not detect vehicle speed it will throw DTC P0500.

Connectors and junction blocks for power, ground and signals for the circuit are are inside the vehicle. The speed sensor is the only thing outside.

[TheJake]

Originally Posted by RogueRider

If the ECM does not detect vehicle speed it will throw DTC P0500.

RogueRide,

Thanks, for the detailed description. One more question. With a DTC P0500 shouldn't the MIL come on. I am not getting a Malfunction Indicator with this one.

Thanks again,
Todd

[RogueRider]

Originally Posted by TheJake

RogueRide,

Thanks, for the detailed description. One more question. With a DTC P0500 shouldn't the MIL come on. I am not getting a Malfunction Indicator with this one.

Thanks again,
Todd

Yes. Diagnostics Trouble Code Chart for Automatic Tranmission indicates MIL light up on P0500 DTC. I'm not absolutely sure on the signal conditions the ECM needs to sense to set P0500. It may take a short or open fault. Poking around in the repair maunual leads be to believe that is the case. You may not be getting P0500 because there is a signal getting to the ECM. We just don't know if it is the same bad signal as indicated on the speedo or not. PM me and I'll try to send you more details on the circuit.

[tinik]

Originally Posted by TheJake

I only question this solution because:

1. I know very little about how this system is designed.
2. It seems very coincidental too have occurred just after I pressure washed the engine.
Is there a junction/connection coupling between the speed sensor and the speedometer that could have gotten wet/damaged during the pressure washing of the engine compartment? I only know that there are three (3) wires connected to the sensor and they disappear into the wiring harness maze shortly after that.

It is odd that the speedo still moves up OK for the first 10 or 15 mph like it should, but then it starts to stutter and hangs around 30 - 35 mph, and it always starts to drop back down when slowing down below where it is stuck and always returns to 0 mph when stopped.
Maybe it is the speedo and it got shorted out because of something getting wet somewhere else… like I wrote, I Know very little about the system, just trying to get as much info before I start tearing apart things.

Thanks for all of your help,
Todd

Speed sensor is located under your SUV at the end of A/T. And connections are well protected from water and snow. Even if you wash your car and engine bay with P/Washer, speed sensor should not be affected.

Only reason I say your speedometer needs to be replaced:
ODO function properly (mileage keep accumilating when you drive)
Most of the cars have same system for ODO and Speedo, so if one works, and the other one have issues, then its speedo problem.

[TheJake]

Thanks for everyone’s help. Hopefully over the holidays I will have some time to poke around and post back what I find out.

Thanks again,
Todd