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Code P0500 cruise control intermittent not working and problem upshifting

Tiny
BOBCONNORS1949
  • MEMBER
  • 1999 TOYOTA CAMRY
  • 2.2L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 196,000 MILES
Hello,

My car developed a problem upshifting and cruise control not working sometimes several months ago. Code is P0500 Speed sensor A. I changed the speed sensor and problem persists. The Speedometer is not malfunctioning and has worked perfectly throughout this before and after I changed the speed sensor. However if I disconnect the electrical connector from the speed sensor then the speedometer does not work at all-- stays at 0 MPH.
I saw a previous similar question answered by your experts that suggested a diagnostic algorithm. So I followed that.
Again speedometer is not malfunctioning. I took the instrument cluster out and inspected the wiring and connectors and they look OK. Next the algorithm said to
" Using DVOM, back probe
ECM harness connector. On models with engine immobilizer system,
measure voltage between ground and terminal No. 8 (violet/white wire) at
ECM harness connector E7. See Fig. 3. On models without engine
immobilizer system, measure voltage between ground and terminal No. 9
(violet/white wire) at ECM harness connector E7. See Fig. 2. On all
models, observe voltage reading while rotating front wheel. Voltage
should pulse between zero volts and 4.5-5.5 volts. If voltage is as
specified, replace ECM. If voltage is not as specified, repair open or short
in wiring between instrument cluster and ECM."
I assume back probe means stick the probe into the connector while it is plugged into the ECM? I did not get the pulsing voltage as described, and the wire was purple but I did not see a white stripe.
The wiring and connectors around the ECM also look okay. Is it possible there is an open circuit in the instrument cluster so that the signal is not getting transmitted? I have attached the original question and answer I referenced.
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Tuesday, March 23rd, 2021 AT 2:45 PM

7 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
The first thing we need to do is get the speedometer working again. here is a video to help you with that:

https://youtu.be/OjUjEnych2s

Next turn the key on and lets check all fuses. here is a guide to help with the fuse location in the diagrams below:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.

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Thursday, March 25th, 2021 AT 10:56 AM
Tiny
BOBCONNORS1949
  • MEMBER
  • 4 POSTS
Fuses are okay. As I said in the original post the speedometer IS working and has not been a problem both before and after changing the speed sensor. The only time the speedometer does not work is if I disconnect the electrical connector on the VSS on purpose just to test. It is the cruise control and transmission shifting that is the problem. So I suspect the signal is getting to the speedometer but not any further. The problem is after the speedometer. My understanding is that the VSS signal goes first to the speedometer and then over to the ECM which then sends the signal to the transmission and the cruise control.
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Thursday, March 25th, 2021 AT 1:06 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Yep sorry about that, so the speedometer works and you have a code saying it doesn't when this happen the ECU is not monitoring the function and should be replaced. Here are instructions on how to do so. Check out the diagrams (below). Please let us know what happens.
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Friday, March 26th, 2021 AT 9:18 AM
Tiny
BOBCONNORS1949
  • MEMBER
  • 4 POSTS
Thanks for the updated reply.
Before I replace the ECU what do you think about the test described below? It is from one of the experts at your site in response to a similar problem on a 1999 Camry.

Using DVOM, back probe
ECM harness connector. On models with engine immobilizer system,
measure voltage between ground and terminal No. 8 (violet/white wire) at
ECM harness connector E7. See Fig. 3. On models without engine
immobilizer system, measure voltage between ground and terminal No. 9
(violet/white wire) at ECM harness connector E7. See Fig. 2. On all
models, observe voltage reading while rotating front wheel. Voltage
should pulse between zero volts and 4.5-5.5 volts. If voltage is as
specified, replace ECM. If voltage is not as specified, repair open or short
in wiring between instrument cluster and ECM."

When I did this test there was no pulsing voltage at the specified connector. Does this mean the VSS signal is not getting to the ECM? Thanks for your input.
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Friday, March 26th, 2021 AT 9:33 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

If you are not getting a signal from the VSS, either the sensor is bad (and I realize you replaced it) or there is an issue with the wiring. Have you checked for continuity between the VSS and the combination meter? Disconnect the VSS and the combination meter and check the VSS signal wire for continuity. Move it around to see if there is something broken or shorted.

If there is continuity in the wire, chances are it is the ECM. If you look at the attached pics, it shows a general diagnostic for the code you have.

Also, you are correct that the signal goes to the combination meter first and then to the ECM. Thus, what Ken expressed is likely accurate.

Let us know.

Take care,
Joe

See pics below.
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Sunday, March 28th, 2021 AT 8:26 PM
Tiny
BOBCONNORS1949
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  • 4 POSTS
Took my car to a shop. Both mechanics with Toyota experience opined that the printed circuit on the back of the combination meter could be the problem since the problem was somewhat temperature dependent. It would happen when first driving but would usually go away after driving awhile especially in hot weather. So I took a chance and put in a used combination meter (instrument cluster). Lo and behold it solved the problem ! I also learned that the combination meter that was in my car was not the original- it did not have the auto trans indicator lights between the temp and fuel gauges like the replacement did so it was for a manual transmission model. Thanks for your help solving this problem.
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Thursday, July 1st, 2021 AT 3:50 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Thanks for getting back to us and letting us know the problem. That makes perfect sense. If it happened only when cold, there was likely a cracked solder joint in the circuit. Once it got warm enough, there is an expansion and the connection changed and worked for you.

Regardless, thanks again for the update. Also, please feel free to come back anytime in the future if you have questions. You are always welcome here.

Take care,

Joe
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Thursday, July 1st, 2021 AT 9:03 PM

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