98 Camry v6 intermittent speedo problem

[DocDave]

Would really like to get some help with this problem as it is driving me nuts!

The problem is that during normal driving the speedo needle will suddenly either drop to zero or bounce around between zero and the speed you were doing before the problem and then drop to zero. This would just be annoying but the car is an auto and once the speedo hits zero the computer thinks you must be stopped, so it drops a few gears, even if you are really travelling at 100km/hr :o. After the speedo hits zero the check engine light comes on and the overdrive off light starts flashing. The speedo may come back to life in a few seconds or after an hour and there seems to be no rhyme or reason to when the problem occurs.

I have a Haines manual so I followed their advice and back probed the vehicle speed sensor VSS in the transmission and it shows power to sensor and alternating voltage output when the problem occurs (tested while driving). I back probed connectors from the VSS to the rear of the instrument cluster and VSS output voltage was still present during the fault. I visually inspected back of cluster and tested continuity of traces from connectors to speedo gauge itself, no cracks etc that I could see. I took speedo out and could find no cold joints etc.

Because there was sensor output apparently all the way to the speedo, I figured that the speedo was at fault and replaced it. No dice, still has same fault.

Now I am stuck, the manual suggests that the only other part that could be at fault is the computer. If I knew that either the VSS or computer was definitely the issue I wouldn't mind replacing, but since I am out the cost of the speedo already I am loath to buy another part until I can at least narrow down the faulty part (if it is a part).

Toyota dealers have been no help since it is an intermittant problem, they say it has to be showing the fault when it arrives at the workshop!

Appreciate any help.

[Ronnyboy]

First thing id do is take the car to the dealer and get it checked.

If the gears are dropping when the speedo drops to 0 km then its probably something to do with the sensors or when the transmission.

Usually when the Overdrive light flashes its got to do with the Transmission/Gearbox

Get it checked before it ends up costing you thousands :(

[DocDave]

First thing id do is take the car to the dealer and get it checked.

If the gears are dropping when the speedo drops to 0 km then its probably something to do with the sensors or when the transmission.

Usually when the Overdrive light flashes its got to do with the Transmission/Gearbox

Get it checked before it ends up costing you thousands :(

Thanks for your response.

I have taken it to the local dealers and they downloaded the error code from the computer. However, the error covers 4 possibilities

- open or short in speed sensor circuit

- vehicle speed sensor malfunction

- instrument cluster malfunction

- PCM (powertrain control module) malfunction

Since it is intermittent the dealers say I have to bring it in when it is malfunctioning. When it does malfunction it may do so for one minute or one hour and when ignition is turned off then on again the problem may or may not still occur, so how to arrange for the dealer to inspect it when it is in the fault condition is just about impossible.

If the problem was a failed part I'm sure that diagnosis would be simple but as it is intermittent you never know when it is going to occur.

Actually, reading my dot points above I have eliminated the first two options and possibly the third, leaving the PCM, but how does one test that? Perhaps what I need is a known good PCM that I can swap in to eliminate it as the source of the problem, anyone have one lying around?

[Ozzcaddy]

Hi DocDave,

One of the members provided me this link http://www.camrystuff.com/index.php?page=Gen4_Manuals where you can download for Toyota Gen4 (1997-2001) Camry Repair Manuals. There is a wealth of information, troubleshooting/dianosing and step by step instruction. If you haven't already done so, you might want to try these, or at least the repair manual that may deal with your speedo problem. They are written for the US but still applicable in most cases.

The Manuals cover both (1MZ–FE) and (5S–FE), so make sure your looking at the correct section.

Edited August 10, 2010 by Ozzcaddy

[DocDave]

Hi DocDave,

One of the members provided me this link http://www.camrystuff.com/index.php?page=Gen4_Manuals where you can download for Toyota Gen4 (1997-2001) Camry Repair Manuals. There is a wealth of information, troubleshooting/dianosing and step by step instruction. If you haven't already done so, you might want to try these, or at least the repair manual that may deal with your speedo problem. They are written for the US but still applicable in most cases.

The Manuals cover both (1MZ–FE) and (5S–FE), so make sure your looking at the correct section.

Hi Ozzcaddy. Many thanks for the link, I'll have a dig around and see if there is anything there that might help. Just going through the process of setting the problem out for others has given me some more ideas for troubleshooting this speedo fault.

The speedo problem is taking a backseat at the moment as the car is up on stands while I replace the front brake pads and have the discs machined.

Thanks again for the help.