hornetball

iTrader: (4)

My EBC stopped working the other day, and I traced the problem to the TPS. The TPS reading still responds to throttle input, but the values are a fraction of what they were before.

I checked the wiring harness and everything inside the MS . . . no issues so far as I can tell. I also checked the resistances of the TPS and they seem strange to me. I get the following:

Orange (O) = 5V reference
Black (B) = Ground reference
Green (G) = ECU pickoff

O-B = 22.2kΩ always
O-G = 21.9kΩ (resting) to 18.7kΩ (fully turned)
B-G = 316Ω (resting) to 3.5kΩ (fully turned)

The direction of resistance movement checks out as do the total resistances at the resting and turned states. The resistances at the resting state look normal to me. However, I would have expected O-G to be much lower and B-G to be much higher in the fully turned state.

Anyone know what resistances I should be reading here? Is it time for a new TPS (this one's been on the car for 2.5 years)? Don't want to waste money if it's operating correctly.

hornetball

iTrader: (4)

Doing the basic voltage divider thing, I'm calculating 0.07VDC at rest and 0.16VDC fully turned at the green wire. That's a far cry from the 0 to 5VDC I should be getting. Guess I'll go ahead and order a TPS. Can anyone confirm?

Braineack

iTrader: (62)

are you getting 5v on your orange wire from the ms?

nitrodann

LOL, 10/10 obvious question.

Sometimes you just need a second mind involved

Dann

hornetball

iTrader: (4)

Yes. I verified wiring as follows:
1. I have continuity from orange to pin 1N. With ignition ON, I get 4.75VDC on orange.
2. I have < 0.1ohms resistance between black and a test point on the engine block.
3. I have continuity from green to pin 2L.

Note that for pin 1N and 2L, I followed Matt's MSPNP directions (swapped from the sticky). It's been working fine for 2.5 years.

Even with the above, doing the voltage division with my current TPS resistance values gives extremely low voltage on green for WOT -- which corresponds to what I'm reading on the computer. If anyone has an undamaged TPS201 sitting around (or could pop the connector off one on the car) and tell me what resistance they get between G-O and G-B, it would give me either a warm fuzzy or stomach acid.

Braineack

iTrader: (62)

that would require effort! maybe when i go move my sprinkler which is getting water all over my miata right now.

hornetball

iTrader: (4)

Well, we wouldn't want that!

Just went to the zone and picked up a TPS4185. TPS201s seem to be getting harder to find locally. TPS4185s were used on mid-2000 Kia's so are in the heart of what the zone would stock locally -- at least for a few more years.

Resistance values from the TPS4185:

+5VDC to GND: 1940Ω
+5VDC to ECU Pickup: 884Ω@Idle to 2620Ω@WOT
GND to ECU Pickup: 2610Ω@Idle to 876Ω@WOT

Based on the above, I'm 99.9% sure that I've suffered a high resistance failure on the +5VDC side of the TPS201. And, yes, I checked for a cold solder joint at the orange wire . . . no such luck.

TPS4185 is looking pretty promising though. Has the correct connector and shaft fitting. Only problem is that I might have to reverse +5VDC and GND in the car harness . . . unless the MS calibration can automatically compensate for that. Standby . . . I'm feeling a write-up with pictures coming on!

FRT_Fun

iTrader: (19)

The MS can't reverse the signal, I looked for a bit since I reversed my ground and 5v ref initially. Just swapped and was good to go.

hornetball

iTrader: (4)

Actually, it "sort of" can. Just did it (had to write my own throttlefactor.inc file to handle the inverse ordering). It worked great for TP%. But the TP% lookup comes after ADC (used by idle logic) and v/s (used by accel enrichment). Bottom line, interesting intellectual exercise but utterly pointless.

Commencing wiring harness surgery now (sigh).

FRT_Fun

iTrader: (19)

Ah yea didn't think of changing up the software. I figured swapping two wires would be easier Odd since I do a lot of programming -.-