Engine No voltage to TPS

3054tony · Nov 13, 2023

Sorry I'm sure it been covered but having a horrible time searching on here.

Car is a 93 GT that has been sitting for a very long time. New battery, starter silinoid, grounds cleaned off, old gas out, new fuel pump, spark plugs, wires, coil, fuel pressure regulator. Car starts right up but horrible idle around 500 RPM, if I give it any gas it will almost die, sputter, backfire but the RPMS will eventually go up. Can have the car holding at 2000 RPMS and as soon as I start letting off the clutch and there is a load it will die. I just checked the TPS but there is 0 volts.

New sensor should be delivered tomorrow but in the meantime if I disconnect it shouldn't the wires going to the sensor have any power?

Car is pretty much stock, exhaust, headers, cold air and underdrive pullies. Eventually I will tear into it a lot more but for now just trying to get it running under its own power so I can move it around and on a trailer to storage for a few months while I'm out of town and house is being built.

AeroCoupe · Nov 14, 2023

With the ignition key in the on position you should see around 5.0 volts on the voltage reference wire (orange). At idle you want around 0.85 volts and at wide open throttle it should be 3.7 volts or higher. You may have to slot the holes on the TPS to get the key on engine off (read throttle body closed) at the 0.85 volts.

Post #1 is a good read and Post #2 is the base idle reset.

Help me create the "Surging Idle Checklist"

Updated 05 July 2022 to add rough idle when cold and smooth idle when up to normal operating temperature. See the EGR tech information, section #15 for more help. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank...

stangnet.com

3054tony · Nov 14, 2023

AeroCoupe said:
With the ignition key in the on position you should see around 5.0 volts on the voltage reference wire (orange). At idle you want around 0.85 volts and at wide open throttle it should be 3.7 volts or higher. You may have to slot the holes on the TPS to get the key on engine off (read throttle body closed) at the 0.85 volts.

Post #1 is a good read and Post #2 is the base idle reset.

Help me create the "Surging Idle Checklist"

Updated 05 July 2022 to add rough idle when cold and smooth idle when up to normal operating temperature. See the EGR tech information, section #15 for more help. Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank...

stangnet.com

Thanks for that diagram, that's what I couldn't find. There is no power at all getting to the sensor itself. Just used a multi meter to check continuity in the wire from pin 5 on the salt and pepper shaker to the sensor and that tested good.

Guessing next step is to pull the connector at the ECU and test for continuity between the shaker and computer.

Would you or anyone know if there is a different diagram for 92-93? The one I keep seeing is 88-91 or are the pins the same?

AeroCoupe · Nov 14, 2023

http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

3054tony · Nov 14, 2023

AeroCoupe said:
This is what I have for my 93:

View attachment 715657

Thank you sir. Looks like pin 47 to me, will have to pull ut out tonight or tomorrow and take a look

AeroCoupe · Nov 14, 2023

I edited that post as I was not 100% sure on the one I have on my external HD. The one I linked I would trust a lot more and yes its PIN 47.

3054tony · Nov 14, 2023

AeroCoupe said:
I edited that post as I was not 100% sure on the one I have on my external HD. The one I linked I would trust a lot more and yes its PIN 47.

Alright I got continuity between the salt and pepper shaker connector pin 5 to pin 47 on the computer. Guess ill send the computer off to be checked out

3054tony · Nov 14, 2023

Not sure if this capacitor has anything to do with it but doesn't look too good anyway.

AeroCoupe · Nov 15, 2023

Yeah that's not good regardless.

3054tony · Nov 30, 2023

Just an update, i sent the computer to ECU Exchange but with the holiday it took a little longer. Fingers crossed it was the issue after reading their report

The tech did finish the repair on your computer.

Your computer will be cleaned and sealed for moisture intrusion before returning.

Your computer had a bad power supply which created distortion on the reference and system voltages. This is due to age and not caused by anything in the vehicle.

There was also some small physical board damage that needed to be repaired.

We replaced the power supply, capacitors and voltage regulators. The computer is now fully functional and running properly.

You can install the computer upon return and start as normal. it did fail on its own due to age.

3054tony · Dec 5, 2023

Well was not the computer. It looks great, they were great to deal, and fixed other issues but not this one. Any other suggestions?

AeroCoupe · Dec 5, 2023

Have you verified that you have 5.0 volts from the ECU (Pin 26) to the white ten pin connector (Pin 2)? If you have voltage to there then you need to chase it to the TPS. It also goes to the EGR valve and barometric pressor sensor so check and see if you have voltage there. It sounds like a bad connection or broken wire at this point.

This diagram is for the engine controls for the 91-93 5.0:

Mustang5L5 · Dec 5, 2023

AeroCoupe said:
Have you verified that you have 5.0 volts from the ECU (Pin 26) to the white ten pin connector (Pin 2)?

I was about to say the same thing.

First thing i'd do is verify your Vref 5V+ and signal ground (pin 46) at the ECU and then trace it out to the TPS. First place i'd check is at the ECU 60-pin connector, and then i'd check at the 10-pin connectors.

3054tony · Dec 5, 2023

AeroCoupe said:
Have you verified that you have 5.0 volts from the ECU (Pin 26) to the white ten pin connector (Pin 2)? If you have voltage to there then you need to chase it to the TPS. It also goes to the EGR valve and barometric pressor sensor so check and see if you have voltage there. It sounds like a bad connection or broken wire at this point.

This diagram is for the engine controls for the 91-93 5.0:

I am not getting anything to pin 26 on the connector for the ECU. I am getting 12 volts to pin 10 on the white connector pictured. Haven't tried the Egr volts yet but both TPS and barometric pressure sensors have no power to them.
Does the #2 pin on the 10 pin connector connect to the #26 pin for the ECU? It's cold and rainy out and might have been rushing and might have checked the 26 on the connector while the 10 pin was unplugged.

3054tony · Dec 5, 2023

Mustang5L5 said:
I was about to say the same thing.

First thing i'd do is verify your Vref 5V+ and signal ground (pin 46) at the ECU and then trace it out to the TPS. First place i'd check is at the ECU 60-pin connector, and then i'd check at the 10-pin connectors.

The white 10 pin connector has 12 volts to the #2 pin but no power to the TPS. I did do a connectivity test with a multi meter from the TPS to the 10 pin connector and from the 10 pin connector to the 47 pin on the ECU and no breaks found. 60 on the ECU is a ground correct? I am pretty bad with electrical stuff but how do you go about testing grounds on a multi meter? I do have a test light if that could be used instead.

Mustang5L5 · Dec 5, 2023

Orange/white wire : pin 26 5 vRef
Black/white: pin 46 sensor ground
Dark gree/light green: pin 47 tps signal to ECU

Pin 26 to pin 46 is what you want to test for 5v. Test it at the ECU and then at the 10pin.

You’ll also want to check continuity of pin 26 and 46 from the 60 pin connector to the tps sensor plug as well with the ECU and tps sensor removed.

3054tony · Dec 5, 2023

Mustang5L5 said:
Orange/white wire : pin 26 5 vRef
Black/white: pin 46 sensor ground
Dark gree/light green: pin 47 tps signal to ECU

Pin 26 to pin 46 is what you want to test for 5v. Test it at the ECU and then at the 10pin.

You’ll also want to check continuity of pin 26 and 46 from the 60 pin connector to the tps sensor plug as well with the ECU and tps sensor removed.

Thanks will test them out tomorrow when I have some more light.

3054tony · Dec 6, 2023

Mustang5L5 said:
Orange/white wire : pin 26 5 vRef
Black/white: pin 46 sensor ground
Dark gree/light green: pin 47 tps signal to ECU

Pin 26 to pin 46 is what you want to test for 5v. Test it at the ECU and then at the 10pin.

You’ll also want to check continuity of pin 26 and 46 from the 60 pin connector to the tps sensor plug as well with the ECU and tps sensor removed.

KOEO pin 26 to 46 has no volts

Mustang5L5 · Dec 6, 2023

Weell you need to have the ECU plugged in, have the key to ON and back probe the 60-pin connector.

You can test continuity with the ecu disconnected but you'll need it plugged in and key on for voltage.

3054tony · Dec 6, 2023

Mustang5L5 said:
Weell you need to have the ECU plugged in, have the key to ON and back probe the 60-pin connector.

You can test continuity with the ecu disconnected but you'll need it plugged in and key on for voltage.

Gotcha ok sorry I didn't know that. Was thinking it should be sending power to the 26 pin with just the key on. I'm horrible with electric .

So ECU plugged in, power should be going to the ECU then ECU should be sending 5 volts to pin 26? Also while plugged in pin 47 should have 5 volts to the TPS?

Engine No voltage to TPS

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