1G DTC 14 Throttle position circuit malfunction

[river]

First off, the car is a 1990 model.

Getting code 0014. I tested the TPS and it's within spec. The closed throttle switch works. Now I'm getting into the wiring harness and it's really frustrating me. There are 4 pins and wires going to the connector.

1 2
3 4

Can somebody please help me figure out what I need to do to test the harness in the car?

With the ignition ON and the car not running I am not getting 5v on any of the wires.

I don't know what more testing to do, and these FSM wiring diagrams are giving me a headache. I'm no electrician and I don't claim to be...but this circuit malfunction is really preventing me from enjoying the car.

 

[liquidz28]

hmmm, have you tried testing it when someone is putting their foot on the gas?
you will get a 0% reading unless someone depresses the pedal, at least thats how it is on my 2g. no power anywhere untill that pedal is pressed.
then again, my car runs just fine w/o it even plugged in...

 

[river]

Yes, I've watched it live in DSMLink and it registers at 0 all the time.

I was tired last night and had a lot more information to include, but couldnt put it into words cause of how tired I was. Tonight I'm going to do some more testing and hopefully it's a bit more conclusive. I'll keep this updated, but my question still stands...

How do you test the connector in the wiring harness? There has to be a ground, 5v signal wire, but what are the other two wires? I'm pretty sure one goes to the closed throttle switch, but that still leaves one wire unidentified.

Wheres wiseman Steve...he'd know how to test this circuit and find the fault.

 

[liquidz28]

mine randomly drops to 0% on my safc also, dosnt change how the car is running at all though, its possable that the plug itself is worn out, thats what i found was my problem, it just rattles to the point where theres no decent connection.
have you visually inspected the tps?

 

[river]

I visually inspected the TPS, yes...but more importantly, I ohm tested the TPS and it checks out just fine.

My problem resides in my wiring harness, or the ECU...and since it's a a re-worked ECU from the guys at DSMLink, I'm doubting the ECU is faulty. That's why I'm wanting to test the wiring between the harness plug and the ECU/grounds. I just dont know where and how to test that wiring.

 

[steve]

Since it's a 90 you really need the 90 FSM since that's the only place some of this is documented.

It looks like at the 4 pin connector you have 3 wires that run to the TPS and 1 that goes to the IPS.
The IPS wire is green and goes to pin 1.
The TPS +5v sensor power is green/red and goes to pin 3.
The TPS sensor ground is green/black and goes to pin 2.
The TPS output is green/white and goes to pin 4.

Needless to say you should have 5v on green/red wire, 0v on the green/black wire and nothing on the green/white if the TPS is disconnected. Once connected you should see between 0.48v and 0.52v when the throttle is closed and around 5v at WOT. If you not seeing 5v on the sensor power wire you may have a bad ECU, bad connector/wiring, or a problem with the MAF which shares the sensor power with the TPS.

The green IPS wire should have about 12v on it when the throttle is opened slightly and close to 0v when it's closed assuming the throttle body is grounded correctly and the IPS switch works.

 

[river]

After doing some testing I am pretty positive the harness is messed up. I'm too lazy to trace it all, so I'm going to just replace the harness. Once the old harness is out of the car I should have my full 1990 service manual, so I'll do some tracing and figure out what's wrong with it. If the new harness I'm getting doesnt fix the problem, then my problem is the "new" ecu I got and I'm going to have to replace that.

 

[steve]

Good luck. To me swapping the whole harness is a lot more work than checking continuity of 4 wires back to the ECU.

 

[river]

Well, you're right...but I'm having difficulties in knowing that I'm checking the right pin # at the ECU. I also was not seeing 5v on the red/green wire like I should have been. I was getting so frustrated doing the tests that my notes are garbage. I'll do the tests again tonight and try to get good notes to you.

Should I be checking:

The IPS wire is green and goes to pin 1. -CHECK CONTINUITY TO PIN # 14 ('90)?

The TPS +5v sensor power is green/red and goes to pin 3. - CHECK CONTINUITY TO PIN #??

The TPS sensor ground is green/black and goes to pin 2. - CHECK CONTINUITY TO PIN # 17 or 24?

The TPS output is green/white and goes to pin 4. - CHECK CONTINUITY TO PIN # 19?

 

[steve]

The TPS +5v sensor power is green/red and goes to pin 3. - CHECK CONTINUITY TO PIN #??

ECU pin 23

The TPS sensor ground is green/black and goes to pin 2. - CHECK CONTINUITY TO PIN # 17 or 24?

ECU pins 17 and 24.

 

[river]

Thanks Steve. I'll do these tests tonight again and see what I come up with.

 

[river]

Forgive my ignorance, but I did all the testing last night and my results are so far off from what they should be that it lead me to think whether or not the pinout image I was looking at is for the actual ECU pinouts or what the pins are on the harness.

Is this looking at the ECU, or the harness?

You must be logged in to view this image or video.

 

[river]

If that's looking at the ECU, then I need to be looking at and testing the harness like;

------------------------TOP--------------------------

12--11--10--09--08--07--06--05--04--03--02--01

24--23--22--21--20--19--18--17--16--15--14--13

 

[steve]

Try reading http://www.dsmtuners.com/forums/articles-tuning-ecu/246467-how-identify-ecu-pin-numbers.html

 

[river]

Sigh. Ok, well...damn. Back to work.

 

[river]

FYI. I swapped harnesses and that fixed the problem. I do not know where the actual issue was in my old harness, but now with it out I'm going to take it apart and replace all the wiring and remove what I don't need.

Only problem the car has now is a high idle. I'm junking the 90 throttle body, going to 91+ and doing the ISC/FIAV delete. That should fix the last issues the car has, and I can finally start enjoying it again!

 

[steve]

I find that a working ISC and FIAV makes the car much more enjoyable. Specially at this time of the year when it's cold and I want the car to start.

 

[river]

My car maybe gets 1000 miles a year put on it. It got less than 200 this year. I don't care about cold startup issues. I just want to eliminate as many un-needed sensors and plugs as possible. The less there is on the car, the less there is to troubleshoot and wait for failure with. I'll keep the lower half of the TB and the ISC just in case, but either way, the FIAV is for sure getting blocked off. I'm positive that the FIAV and/or ISC are stuck open right now and that's what's causing the high idle.

 

[ENICKB]

so will the car run just the same with or without the TPS? Because i am getting the tps circuit malfunction and im thinking to just get rid of it, any thoughts? is it needed? i have no isc or fiav. its all blocked off.

 

[93_tsi_fwd]

It will run fine with it unplugged but its need for tuning and tells the ecu on how much fuel to throw in the motor. If its not working, Its counting on the O2 sensor on how much fuel to give the motor and sometimes its not that accurate.

 

[steve]

With it unplugged or missing the ECU will be in limp mode all the time.

 

[ENICKB]

With it unplugged, it definitely runs like POOP. I am trying to fix this problem. I have a new throttle body on here, and it has a 4 pin TPS on it. But although my wiring harness fits the TPS perfectly, it has the same connector, but only 3 of the 4 pins for the tps. From the bottom to the top it has green-red(+), green-white(tps), EMPTYSPACE(?), green-black(-).. I was wondering if this could be the source of my CEL that I get under cruising 0014. But I read in similar forums that the EMPTY SPACE is green-blue, and it is for an idle switch. But I have an idle switch on the throttle body, so maybe its the wrong tps? I only have one vaccum on the TPS, so I think its a 2g. So is it bad to have a 4pin tps, plugged into a harness with only the 3pins plus an empty space, while running an idle switch, or maybe I have a faulty TPS?

 

[steve]

There is nothing wrong with using a 2G TPS if the connector fits. Adjust it as you would a 1G by output voltage and make sure that your throttle body is grounded so that the IPS on the back can work.

 

[assassin3117]

Base Ignition Timing [1] 5°+/- 2°BTDC at idle

Fuel Injector Coil Resistance (NON-TURBO)


At 20°C (68°F) 13 - 16 Ohms

Fuel Injector Coil Resistance (TURBOCHARGED)


At 20°C (68°F) 2 - 3 Ohms

Fuel pressure control valve [1]


At 20°C (68°F) 36- 44 Ohms

Idle Speed Control Servo Resistance


At 20°C (68°F) 28 - 33 Ohms

Throttle Position Sensor Adjustment Voltage


At curb Idle 0.48 - 0.52 Volts

Throttle Position Sensor Resistance 3.5 - 6.5 Kohms

Wastegate solenoid valve [1]


At 20°C (68°F) 36- 44 Ohms

[1] Turbocharged models only.


Throttle Position Sensor Circuit






CAUTION: Before attempting to adjust the Throttle Sensor, make certain the idle speed and ignition timing are correctly adjusted. See this section for the proper procedures.

Requirements before adjustment:



Engine fully warmed up. (185°- 205°F)
All lights, engine cooling fan and accessories "off".
Transmission in P or N.
Steering wheel in the straight ahead position (models with power steering only).
Verify that the throttle cable has enough slack that it is not holding the throttle open in any way. Loosen the adjustment bolts for the throttle cable if necessary.
Using a high-impedance digital Voltmeter, carefully back probe the throttle position connector into terminals #3 and #4.
Turn the key to the ON position.
Check the output Voltage of the TPS.
Voltage
0.48 - 0.52 VDC

If necessary, adjust the TPS by loosening the mounting screws and rotating the sensor. Clockwise rotation of the sensor increases the Voltage output while counter-clockwise rotation reduces Voltage.



Tighten the sensor set screws securely.
Turn the ignition switch OFF.
Disconnect the battery for at least ten seconds to clear any stored trouble codes.
If the throttle cable was previously loosened, return the cable to the proper adjustment.

Here is an image to go with the info I posted.