Overdrive issues. Please help.

[Guest Dikachim]

Alright, I need all the help I can get please.

I have a California spec US 93 NA Supra Auto. Completely Stock.

 

Problems:

My odometer and Tach work but my Speedometer doesn't.

My cruise control light shows up but doesn't work.

My car doesn't seem to go into overdrive so i have very high revs while not going any faster than a Toyota Yaris.

The display where oil pressure, check engine and co are, don't light up at all at any time.

Also the manu button on the auto used to come on sometimes when I pressed it. Now it does nothing.

I used to have intermittent o/d off flashing but haven't seen it since I did the speed sensor splice.

I do have other issues like power door and side mirrors not working well but these aren't really important.

 

What I've tried:

The popular speed sensor splice(seemed to improve low speed shifting issues).

I've examined the speed sensor at the transmission, looks normal although I wouldn't know what it's supposed to look like.

I've opened up the dash to check for any loose connections behind the speedometer and didn't see any.

 

Please help I don't want to go throwing money at these issues yet. I'm burning a lot of fuel while driving a very slow car.

P.S I'm not in the UK.

 

Thank you.

[Guest Dikachim]

Can anybody help please? I still have this problem.

 

Alright, I need all the help I can get please.

I have a California spec US 93 NA Supra Auto. Completely Stock.

 

Problems:

My odometer and Tach work but my Speedometer doesn't.

My cruise control light shows up but doesn't work.

My car doesn't seem to go into overdrive so i have very high revs while not going any faster than a Toyota Yaris.

The display where oil pressure, check engine and co are, don't light up at all at any time.

Also the manu button on the auto used to come on sometimes when I pressed it. Now it does nothing.

I used to have intermittent o/d off flashing but haven't seen it since I did the speed sensor splice.

I do have other issues like power door and side mirrors not working well but these aren't really important.

 

What I've tried:

The popular speed sensor splice(seemed to improve low speed shifting issues).

I've examined the speed sensor at the transmission, looks normal although I wouldn't know what it's supposed to look like.

I've opened up the dash to check for any loose connections behind the speedometer and didn't see any.

 

Please help I don't want to go throwing money at these issues yet. I'm burning a lot of fuel while driving a very slow car.

P.S I'm not in the UK.

 

Thank you.

[stevie_b]

That's a lot of electrical issues you have there. It sounds like some or most of your dashboard isn't wired up properly, or has a wiring fault. A bad earth can sometimes cause strange effects as the electrical circuit tries to complete via other components, so you could try running another temporary earth cable from wherever the dashboard earths, to the battery or chassis, but it sounds like you have multiple electrical faults.

 

Any sign of burnt wires when you remove the dash fascia? Are all the fuses OK in both fuse boxes?

 

Is your wiring completely stock?

 

As your odometer works, then the speedometer (unless wiring has been radically altered) will also be getting the speed signal, so no need fo further work at the speed sensor.

Edited May 26, 2015 by stevie_b (see edit history)

[Guest Dikachim]

Thank you for your response. I really appreciate.

 

I don't really understand what you mean by I could try running another temporary earth cable from wherever the dashboard earths to the battery or chassis. Please explain this.

 

I haven't seen any sign of burnt wires when I removed the dash and the fuses all seem OK but I'll check again tonight.

My wiring is completely stock save for an ancient aftermarket head unit and some aftermarket speakers wiring I noticed. Yesterday when i was in the footwell fiddling around for possible clues, I touched a wire junction that seemed to trip the radio off. Touched it again and the radio came back on. The junction felt funny but i didn't look at it. Only felt it. Maybe i'll actually take a look at it also.

 

Yes my odometer works all the time as well as my Tach so I doubt it's the speed sensor and I'm confused about it.

 

One more thing I noticed, the dash lights that indicate what gear you're in, doesn't seem to work all the time especially for P and N. D doesn't work at all.

 

Thanks for your help.

 

That's a lot of electrical issues you have there. It sounds like some or most of your dashboard isn't wired up properly, or has a wiring fault. A bad earth can sometimes cause strange effects as the electrical circuit tries to complete via other components, so you could try running another temporary earth cable from wherever the dashboard earths, to the battery or chassis, but it sounds like you have multiple electrical faults.

 

Any sign of burnt wires when you remove the dash fascia? Are all the fuses OK in both fuse boxes?

 

Is your wiring completely stock?

 

As your odometer works, then the speedometer (unless wiring has been radically altered) will also be getting the speed signal, so no need fo further work at the speed sensor.

[stevie_b]

I don't really understand what you mean by I could try running another temporary earth cable from wherever the dashboard earths to the battery or chassis. Please explain this.

 

All electrical systems in the car will have a wire (an earth wire) connecting it either directly to negative terminal on the battery, or something metal and substantial like the chassis or engine block. The dashboard electrical circuits will probably have a wire, or several wires, connecting it to the metal bodywork. My suggestion was to identify the earth wire in one of the circuits, attach a new piece of wire to it, and attach the other end to the -ve battery terminal or the metal bodywork.

 

E.g. take the speedo cluster as a good example. There will be a green circuit board on the back of it. Identify the earth connection on it (either by searching on here, or by looking at the circuit board's annotations) and run a new wire from it to the -ve battery terminal.

 

This isn't necessarily a trivial thing to do: you might not be able to get good electrical contact for the new earth wire at the circuit end. You might find it hard to identify where to connect the earth wire.

 

You can cause serious damage to you and the car if you go touching wires together that you're not sure what they do. If you're not sure, get someone to help you or take it to an auto electrician.

[Guest Dikachim]

This problem persists. My power mirrors work now but my speedo still doesn't, so no 4th gear for me. This is absolutely frustrating. The auto electricians don't know much about the car and I'm probably the only one that owns one in my city so parts are near impossible. So frustrating

[ScottC]

check the ecu for any fault codes, Remove your speed sensor splice and return the wiring back to stock, reset ecu, take the car for a drive and re check for fault codes. Report Back

[Wendy]

I also had the “no overdrive/ 4 gear transmission issue, no cruise control, odometer not counting, fuel pump ecu and other electrical problems with my 94 Supra. The source causing all my electrical issues was the “ECU” & loose wiring (pins) in the connector / harness that connects to ECU. My mechanic re-pinned the loose wires & replaced several burnt resistors & leaking capacitors & repaired broken traces in the ECU.