Hi, this is my first technical post so please feel free to give your advice;
I have a 1991 RX-7 Non-Turbo. It's throwing 2 codes: 12(Throttle Sensor Full Range "Broken wire, short circuit") and 18(Throttle Sensor Narrow Range "Broken wire, short circuit"). I'm getting all my info from AllDataPro.
These are the "Testing and Inspection" steps I looked up:

Step 1. Are there poor connections at Throttle Sensor connectors?
-The connector is in excellent shape and clicks into place.

Step 2. Is voltage of ECU 2G terminal OK?
-I skipped to step 3 because I don't want to risk frying the ECU.

Step 3. Is there continuity between throttle sensor and ECU?
-I did this yesterday very extensively, even going as far to see if each wire from the throttle sensor has continuity to other pins as well. I also documented all of it on paper for easy reference and double checked all of my readings.

These are my results, including the wire color at sensor end and ECU Pin code. I was VERY careful to verify and double check which wire I was connected to, and tracked back the wire to which sensor as well(Full or Narrow).

CONTINUITY READINGS:

DTC 12: FULL RANGE

(A.) Throttle Sensor Vref(BR/W harness, RED at sensor) to ECU pin 2I:
-FAIL: NO CONTINUITY to 2I, but continuous to 9 other pins on ECU connector 2, and also to others at ECU connectors 1 and 3.
(B.) Ground(BR/BLK, BLU) to 3D:
-PASS?:Continuous to 3D, but also continuous to 20 other pins on the ECU 3 connector, AN D other pins on ECU 1 and 3.
(C.) Signal(BLK/GRN, YEL) to 2G:
-FAIL: NO CONTINUITY to 2G, BUT is Continuous to 2H(the pin right below it). Not continuous to any pins except for 2H.

DTC 18: NARROW RANGE

(A.) Vref(BR/W, ORG) to 2I:
-FAIL: NO CONTINUITY to 2I but IS continuous to many other pins on 1, 2, and 3.
(B.) Ground(BR/BLK, BLK/RED) to 3D:
-PASS?:Continuous to 3D but ALSO to many pins on 1,2, and 3
(C.) Signal(GRN/RED, GRN/RED) to 2F:
-FAIL:NO CONTINUITY to 2F but IS CONTINUOUS to 2E(the pin right above it!). Is not continuous to any other pins.

Maybe some of that data is irrelevant, but I figured I would include all of it. I actually enjoyed doing this, it just took a long time to get a process down. But now I think I can tackle alot more electrical stuff.

ANYWAYS, could a seasoned electrical expert summarize whats going on here? Also what should my next step be?
THANKS!!!

 

W/key to on, the Brown/White wire ought to measure about 5 volts DC on both sides of the TPS connector.

 

Okay, will I be doing that with the sensor connected? I assume so since you say at both sides. And my ground lead should be grounded to the chassis?
Thanks!

 

Yes, the sensor must be connected, and the ground lead of the multimeter placed to an engine ground (negative battery terminal works well).

 

Thanks Satch!
It PASSED that:
Both brown/white wires(which are Vref) measure 5 volts on the sensor sides. I did this by carefully sticking a sewing needle into the insulation and making contact with the wires inside and grounding my NEG Lead to the (-)BAT Terminal.

BUT:
I went ahead and did STEP 2 of the AllDataPro diagnostic procedures:

STEP 2:

FULL RANGE test: Is Voltage of ECU terminal 2G terminal OK?
[Signal wire(B/G, YEL)]

Idle position: Voltage Specification should be 0.25V-1.25V.
-FAIL: Reading @ 0.20V.

Full opening(WOT): Spec should be 4.1V-4.4V.
-PASS: Reading @ 4.25V.

NARROW RANGE test: Is Voltage of ECU terminal 2F OK?
[Signal wire(GRN/RED, GRN/RED)]

Idle position: Voltage Spec should be 0.75-1.25V.
-FAIL: Reading @ 1.51V.

Full opening(WOT): Spec should be "Approx." 5V.
-???: Reading @ 4.59V.

Sooooo, from these readings do I need a new sensor? Also, am I probing the wires at the correct point? And lastly, why are my Continuity readings from the first posting so weird?
Thanks!

 

The voltage tests are to be done w/the engine completely warmed up. Is this how you did it?

 

No, it was about 50 degrees F when I did that test.
But I just did the test right after driving pretty hard for 45 minutes. Here are the results once more:

STEP 2:

FULL RANGE test: Is Voltage of ECU terminal 2G terminal OK?
[Signal wire(B/G, YEL)]

Idle position: Voltage Specification should be 0.25V-1.25V.
-FAIL: Reading @ 0.11V.

Full opening(WOT): Spec should be 4.1V-4.4V.
-PASS: Reading @ 4.21V.

NARROW RANGE test: Is Voltage of ECU terminal 2F OK?
[Signal wire(GRN/RED, GRN/RED)]

Idle position: Voltage Spec should be 0.75-1.25V.
-PASS: Reading @ .91V.

Full opening(WOT): Spec should be "Approx." 5V.
-???: Reading @ 4.6V.

Do I need a new sensor?
And also why would the continuity tests be obsolete?
Thanks again!

 

The air temp really isn't important here but it is the engine temp which is when setting the TPS. If you did the test immediately after driving for 45 minutes then that is clearly long enough.

Measuring at pin 2G is easy to do and you're measuring the Green/Red wire you just measured at the TPS as it is the same wire. Red meter lead to pin 2G and the Black meter lead to one of the four mounting bolts for the ECU for the ground ( two bolts at the front of ECU are obviously the easiest of the four to use).

There are certain tests to measure the functionality of the TPS found in the service manual. Did you follow these tests or did you create your own?

 

Yea when I first did the test the engine was probably about 50 degrees F, but it was all the way warmed up the second time.

Are you referring to the continuity test?
The Full Range Sensor signal wire(BLK/GRN, YEL) did not have continuity to 2G, and the Narrow Range Sensor signal wire(GRN/RED, GRN/RED) did not have continuity to 2F. I am getting these diagnostic instructions from a shop's AllDataPro account.
You're suggesting that I should test the FAILING 2G[Full Range(which is the BLK/GRN wire on the harness, and YELLOW on the sensor wire], for possible continuity to ground, correct?

I am using a shop's AllDataPro account to run these tests and printed them out for easy reference. It's always seemed to be an equivalent to the factory service manual, or could it be different than the FSM?
Thanks.

 

Testing for voltage is not related to measuring for continuity. You just need to see if the reading you get at the sensor's G/R wire is the same as at the ECU. The G/R wire w/key to on and engine fully warmed should read 1 volt.

 

Okay, this is weird.
The 2G wire at the ECU connector is showing 3.49V @ Idle Position AND Wide Open Throttle, AND the 2G wire color is GREEN/YELLOW. The 2H wire(directly below it on the connector) is BLK/GRN though(BLK/GRN is the color on the sensor side but not at the ECU).
Does this explain why the Full Range Signal Wire(BLK/GRN, YEL) had continuity to 2H and NOT 2G(2G is where it's supposed to have continuity to)?
And I just tested the 2H(BLK/GRN) wire at the ECU connector. It IS affected by the throttle position and matches my results for the FULL RANGE test: Is Voltage of ECU terminal 2G terminal OK?
[Signal wire(B/G, YEL)]
Idle position: Voltage Specification should be 0.25V-1.25V.
-FAIL: Reading @ 0.20V.
Full opening(WOT): Spec should be 4.1V-4.4V.
-PASS: Reading @ 4.25V.
These results were taken from the 2H(BLK/GRN) wire at the ECU connector.

The 2H wire at the ECU connector(BLK/GRN) is backwards right? Should I switch the BLK/GRN wire with the GRN/YEL wire thats in the 2G position?

 

I stated pin 2G, but I made an error and should have typed pin 2F. Sorry!

 

It's all good, typos happen. Just like my underlining typo on one of the above tests.

I tested 2G, 2H, 2E and 2F while they were cold and then when warmed up. I think 2G's wire is in the 2H pin, and 2F's wire is in the 2E pin at the ECU connector. This is why I think that and let me know if you agree:

2F @ ECU connector(Narrow Sensor Signal wire):
(GRN/RED @ Sensor connector, BUT is GRN/WHT @ ECU Connector 2F)
Cold test: 2.77V @ Closed Throttle AND WOT(2.77V throughout throttle range.
Warm test: 0.44V @ Closed Throttle AND WOT(0.44V throughout throttle range).
This wire should reflect varying voltage as it does at the sensor, right?

When I saw that I tested the pin directly above 2F which is 2E and is GRN/RED).

2E @ ECU connector:
Cold Test: 1.64V @ Closed Throttle and 4.59V @ WOT.
Warm test: 1.02V @ Closed Throttle and 4.59V @ WOT.

These wires would be backwards based off these readings, am I correct?

The first two pictures are of connector 2(that's a piece of paper wrapped around the 2E and 2F wires so that I could distinguish them from the rest). The third picture is connector 1 but I want to make sure that I am reading the chart correctly and not backwards. You'll notice how the pins match the chart, but the designs on the border are opposite than the actual connector. Does that matter? The pin coordinates can only be one way if you look at how many pins are on the right versus the left(4 big pins on the right, 2 big pins on the left). How it looks in picture # 3 is how I've been reading it to get my test results.

 

Wow. I just realized what I've been doing wrong. I've been reading the ECU pin chart as if it were the connector pin chart. That explains why it looked backwards and why my continuity tests looked weird. Wow. I've been in such a rush to smog and register my car that I somehow overlooked that simple idea. I guess thats why they call it the "New Member Technical Section" hahaha.
I'm sorry Satch, I didn't mean to waste so much of your time. I will adapt my data to the proper wires and review haha.
But to answer your question, correctly:
2F is GRN/RED afterall, and warmed up it's reading:
1.02V @ closed throttle and
4.59V @ WOT.
Sorry Satch!

 

These are the retest readings for Diagnostic Trouble Code 12 and DTC 18. The tests were done correctly(no more upside down pin readings!), with vehicle warmed up between each voltage test.

Step 1. Throttle Sensor Connector Inspection:

Are there poor connections at Throttle Sensor connectors?
The connector is in excellent condition and clicks into place firmly.

Step 2. Voltage Tests:

Code 12(Full Range Sensor)
Is voltage of ECU 2G terminal OK?:
Idle position reading @ 0.09V (Specification Voltage is "0.25-1.25V") FAIL
Full opening(WOT) reading @ 4.20V (Spec. Voltage is "4.1-4.4V") PASS

Code 18(Narrow Range Sensor)
Is voltage of ECU 2F terminal OK?:
Idle position reading @ 0.78V (Spec. Voltage is "0.75-1.25V") PASS(Barely)
Full opening(WOT): reading @ 4.59V (Spec. voltage is "Approx. 5V") ???

(These readings were taken from the ECU Connector side AND the Throttle Sensor Side and are matching in Voltage at both ends. I'm not losing any Voltage through the harness.)

Step 3. Continuity Tests:

Is there continuity between throttle sensor and ECU?
Code 18 and Code 12 PASSED on all 6 continuity tests.
At first I thought I had a bad connection between the harness wires and the connector pins at the ECU because I would get continuity with the wire pushed into the connector, but not when I pulled the wire out slightly. BUT then I determined that this is because the metal pins slide in and out of the plastic connector ever so slightly, in turn not making consistent contact with my test lead. I'm pretty sure they would make contact when the connector is plugged in to the ECU, right?)

I have included pictures of the AllDataPro Diagnostic Charts for DTC 12 and DTC 18 below.

My next step is to tune the throttle sensor to factory specs with my homemade "checker lamp". I have included that AllDataPro attachment as well.
Plus a picture of my S5.
Sorry that I looked like an idiot last week for reading my pinout chart upside down! But I figured it out and that's what learnings all about right?

Thanks again Satch for all your help and let me know if we're still cool haha.

 

The TPS signal at pins 2F and 2G are output signals from the TPS which means they are input signals at the ECU so it is at the ECU where the readings really count because they can be good at the sensor, but not received at the ECU and this causes the error code. The narrow range setting is adjustable by adjusting the TPS screw (1 inch long flat head screw incased in a spring located rnear the throttle kinkage that rests upon the TPS).

 

I bought a used throttle sensor and it fixed the two codes I was getting. The on/off throttle surging at low RPM is gone also. It passed Smog yesterday and had super low Hc. I was surprised, because I didn't do the alcohol trick or really that much of anything at all:
I had 1/8th of a tank of gas, and all I did was warm it up in my driveway for 20 minutes beforehand. I was running half of a small bottle of Lucas Fuel Injector Cleaner, and Arco 87 Octane gas.
Thanks Satch for all your help, I really appreciate it.

 

The alcohol trick is for AFTER you pass...lol!
..you Drink some to celebrate passing!..WOOT!

 

Hey misterstyx, I forgot to say, the alcohol trick worked great! There was a heavy buzz and my alignment was out of spec! I kept leaning to one side haha. It worked quite well!

 

I know that feeling.
I kept on saying "Baby you are so cold and flat chested". Then I realized I was kissing a sidewalk!