97 Camry with defective O/D light Off and poor gas mileage

[Shinto]

I have a 97 Camry that was bought used with 129K and has a horrible gas mileage of about 17m/g. I have been trying to diagnose the problem and these are my initial observations and results:

• A scan tool did not register any trouble codes
• The O/D Off indicator light does not light up when the O/D main switch is pushed out to Off or push in to On.
• I suspect the transmission fails to up shift from third to overdrive due to the malfunction of the O/D.

For starters, I am trying to follow the diagnostic procedure as indicated in DI-428 (Diagnostic manual, page 428). Could someone help me on how to disassemble the center console so I could reach the O/D main switch connector?


I welcome any suggestions and ideas that might help me fix this problem.

[JohnGD]

Check the OD bulb first. If the bulb is good then dig into the switch wiring.

A bad engine coolant temp switch can also mess with up shifts and mileage too. So check that too.

[Shinto]

Thanks for the advice. I don't think the transmission up shifts from 3rd to overdrive. I would check the temp sensor tomorrow. In the mean how can I reach the O/D main switch wiring connector? So far I have been only able to take off the molding with the cigarette lighter switch attached.

Please help me! How do I get to the O/D main switch wiring connector without breaking things.

[Shinto]

This is how far I have been able to disassemble the console around the shift lever. Can someone please direct me on how to reach the O/D main switch?

[JohnGD]

I'm not sure the exact location but is the white connector on the rear side of the shifter the four-wired connector? See if you get open/continuity on two of the wires as you switch on/off the OD switch. The two wires should be on the flat side of the connector. The other end has beveled corners. Not sure harness or wire side however. Sorry don't have more, there doesn't seem to much info on this thing.

[Grzegorz]

I've found on 99'Camry Wiring Diagram pdf file (page 31) O2 connector which refers to O/D Main Switch and A/T Shift Lever illumination. This is on the FRONT of vehicle side of shift lever you showed on your picts. I is not seen on your picts and it is on the OPPOSITE side than white connector we can see on your photos.
However I don't know how to get there since I never went any furher then you currently are.

The following is a name of pdf with corresponding informations:
'99ElectrWiringDiagram.pdf

[Mike Gerber]

This may sound a bit strange, but I have seen poor fuel mileage traced to a weak themostat that is opening way too early or is stuck in the open position. Does the needle on the temperature gage reach the mid position in a relatively short time? If it's barely in the markings on the gage, that could explain both the poor fuel mileage and the fact the transmission is not shifting in to O/D.

Mike

[Shinto]

Thanks to both Grzegorz and Mike Gerber for your contribution. Some problems are so rear that it is very difficult to get members to get give their advice or opinion.

I have located the O/D main switch connector as described by Grzegorz. I measured the resistance and the reading indicates that the switch is good. Now, the problem must be with the "O/D Off" illumination bulb on the instrument panel or the harness.
If the "O/D Off" light fails to come on due to a dead bulb, then that may not have any thing to do with my extremely poor gas mileage.

Mike Gerber and JohnGD both have mentioned the faulty temp sensor link to poor gas mileage, so I would work on that and report back except that may that may take awhile since I am currently several miles away from the vehicle.

[JohnGD]

Check and fix the OD bulb first and see if this restores the shifting. The autoshop101 article on toyota's electronic control transmission suggests the bulb may be part of the circuit. If so that would be a stupid design, but you never know.