TPS Mystery

[Flyn Sy]

I keep getting a code 21 on the SY, which indicates a TPS malfunction (voltage high). The mystery is that it occurs randomly. There doesn't seem to be an degredation of performance or driveablity. It does seem to come on more after I hammer it, but a lot of times just crusin'. The code is generated with high voltage, low voltage, and anywhere in between, acording to the scantool when driving, and statically with a full scale analyzer. The sensor has been replaced, and the ground reset. Wires have been checked, but yet the problem persists. Any ideas?

 

[syco1962]

Re: TPS Mystery

hi, i was getting the same problem what it turned out to be the 3 wires at the tps one had a internal break, bought a pig tail and it solved the problem, try moving the wires when its running see if it stumbles hope this helps

 

[Don W.]

Re: TPS Mystery

With motor off, key on and scan tool recording TPS volts, slowly press throttle to full and back watching TPS voltage. It should follow your foot virtually exactly. Once you do it you'll see what I mean. Watch for anomalies. Maybe have someone wiggle wires at the same time.

HTH

 

[DaveP]

Re: TPS Mystery

I keep getting a code 21 on the SY, which indicates a TPS malfunction (voltage high). Any ideas?

Code 21 will always be caused by a loss of ground at terminal A at the TPS, which is a dedicated ground for the TPS and MAT to terminal B5 at the ECM. So concentrate on the black wire at the TPS, and at pin B5 at the ECM.

Sometimes TPS going high will cause a good crank / no start because the ECM enters Clear Flood mode, and interrupts signal to the injectors.

 

[Logan]

Re: TPS Mystery

Code 21 will always be caused by a loss of ground at terminal A at the TPS, which is a dedicated ground for the TPS and MAT to terminal B5 at the ECM. So concentrate on the black wire at the TPS, and at pin B5 at the ECM.

Sometimes TPS going high will cause a good crank / no start because the ECM enters Clear Flood mode, and interrupts signal to the injectors.

I really hope to have this much SyTy knowledge at some point in my life.

 

[neildemo]

Re: TPS Mystery

Good Luck! Dave is a Godsend to the SYTY world. I bet without his knowledge here a good portion of our trucks would be on jackstands forever.... Can't say this enough...THANK YOU DAVE. :tup::tup:

 

[vinnieTy]

Re: TPS Mystery

I really hope to have this much SyTy knowledge at some point in my life.

I cant agree more!! :tup:

 

[Flyn Sy]

Re: TPS Mystery

AMEN! Thanks Dave, and to all who have responded. Going to put this info to use today. God, I'm glad to be a part of this community!

 

[Sydwinder905]

Re: TPS Mystery

Good Luck! Dave is a Godsend to the SYTY world. I bet without his knowledge here a good portion of our trucks would be on jackstands forever.... Can't say this enough...THANK YOU DAVE. :tup::tup:

Or us techs at the GM Dealers would be having a hell of a time trying to figure some of these issues out!

 

[Flyn Sy]

Re: TPS Mystery

UPDATE:

OK, guys and gals, here it is. When I started this odyssey I stood 6’6” and had a whole head of hair. Now at 5’5” and mostly bald,. I give up. I cannot find the problem with this Code 21 nonsense. Here’s what’s been done:

- Replace TPS 3 times – 1 new, and 2 known good

-Re-grounded TPS by moving ground wire to 2 different locations and at B5, per DaveP instructions

-Replaced entire plug to TPS.

-Welded new ground lug to frame and replaced engine grounds and ran new ground wires/cables to ECU

-Installed a new ECU…..still Code 21 (sent that sucker back). Tried the ECU out of the Ty…..Still Code 21.

-Replace the TurboTweak chip with a TurboTweak chip that was programmed with the same parameters, except for wide band……Code 21.

-Took the TurboTweak chip out of the Ty and installed it……..still Code 21.

-Spun around and clicked my heels 3 times………..still Code 21. If anybody has a stock chip they’d like to sell, PM me. I want to try that, and besides, I’d like to have one sitting around for troubleshooting purposes, in the future.

-DataMaster doesn’t show any anomilies. TPS voltage has never exceeded 4.46v. The Code 21’s happen at random……High speed, low speed, with boost, without boost, over hill, over dale….ei, ei, oh.

-DataMaster records directly before Code21 and directly after, show little or no changes in any engine parameters. Code 21’s happen at random voltages, i.e. 1.28v, .94v, 2.93v, etc.

Driveabilty is NOT an issue. I don't notice any Idling problems or stumbling peformance, nada, zip, zilch.

I’ve searched other sites for anything related to this problem and have found NOTHING!!!! Does ANYBODY have any other suggestions, of should I just get my trusty .44 Mag and shoot out the Check Engine light?

 

[WOTracer]

Re: TPS Mystery

On a whim, could you have a borderline bad Map sensor or bad Map circuit/leak? I read you didn't state a code 33 or 34 but marginal MAP/circuit could perhaps send a code 21. It seems like you covered the whole basis for the TPS......

 

[IGottaSy]

Re: TPS Mystery

In thinking like the ECM, what exactly should be happening when it receives the TPS signal???
I don't know. Please explain. I can think of...

1. Command less fuel at idle/deceleration by decreasing voltage to ??? Injector pulse rate??? Fuel pump voltage???
2. Pulls timing back to match under above conditions and opposite upon acceleration.



ECM is reading tps to be out of range or losing its signal at some point and code is set off.
I am just wondering if there could be problem with throttle body's TPS mounting area that could cause an adverse movement of the sensor. Worn out butterfly rod or something sticking. Not a mechanic or a guru here so take it for what it's worth. Just trying to learn/help/grow to 6.6 feet tall.

 

[WyoSyclone]

Re: TPS Mystery

Sounds like the only possibility may be a break in the wiring somewhere between the TPS plug and the ECM....both wires, 417 (dark blue) and 416 (gray), pass through a grommet on the cowl, not the bulkhead connector, so maybe that would be a spot to check. If I remember correctly, taking the passenger side fenderwell out gives one pretty good access to that grommet.

 

[DaveP]

Re: TPS Mystery

I'm going to ask a really, really, really dumb question. Please forgive me. But I had "this" come up with a guy I was working with chasing a Code 32 EGR in his TPI Corvette.

Are you also getting Code 12? If all you have is the one "Code 21" you are reading the flashes backwards. It's really Code 12, which is normal, everything is Ok.

The guy with the C4 was reading a Code 23 as 32. 23 is MAT High. He had knocked the connector off the sensor on the bottom of the plenum. Took us two weeks chasing 32, even though I knew it couldn't be 32, because the conditions under which it set the CEL.

I'm getting the same feeling about your 21. 21 is very simple. Only a loss of ground to the sensor can cause a 21.

If you're getting BOTH a 12 AND a 21, I'm stumped too.

 

[Flyn Sy]

Re: TPS Mystery

Reading the code on ScanMaster and on DataMaster. Just for laughs, I did read the flashes, and I'm sure it was code 21 flashing after the code 12. Just as a note, we did bypass the whole TPS wiring to the computer, and put all new wiring in. Damn, what a nightmare.

 

[DaveP]

Re: TPS Mystery

-DataMaster records directly before Code21 and directly after, show little or no changes in any engine parameters. The Code 21’s happen at random……High speed, low speed, with boost, without boost, over hill, over dale….ei, ei, oh.
Code 21’s happen at random voltages, i.e. 1.28v, .94v, 2.93v, etc.

Driveabilty is NOT an issue.

I re-read your recap. Your 21 has to be bogus. The conditions for 21 aren't being met.

Paramaters to set Code 21:

• TPS reading above 2.5 V (50% throttle or more)
• MAP below 81 kPa (engine under heavy load)
• Engine speed below 1300 RPM.
• All above conditions present for 10 seconds. (Impossible, unless it's electrical).

Basically, there is no way to have a 2.5 volt TPS and have engine speed below 1,300 RPM for more than 10 seconds. You're setting 21 without meeting the conditions for setting it. This shouldn't happen. Something is wrong with the bin.

Sorry for the accusation that you don't know how to read your flashes.

Something in Eric's bins has to be corrupt. And the bug is affecting all the PROMS of his you've tried. Really weird. Talk to Eric again.

 

[DaveP]

Re: TPS Mystery

Is the Typhoon close enough in configuration to the Sy that you can take the ECM/PROM from the Sy and put it in the Ty and go for a drive? If there's a 2bar - 3bar difference, swap the MAP's too. If you can get the Ty to set the 21, it's not the truck that's setting it.;

Just an idea.

 

[CC801]

Re: TPS Mystery

This may be a bit of a reach, but any chnace there is excessive play in the throttle shaft? The tps is a potentiometer, the pcm is expecting to see a certain voltage in coordination with the map sensor and engine speed. The tps sensor reads minute changes in throttle position. If you had a lot of play in the throttle shaft, as a lot of these trucks do because of worn bushings, then it may be enough to give the pcm a voltage it isnt expecting to see. Just a thougt since youve tried almost everything else.

 

[Flyn Sy]

Re: TPS Mystery

No offense taken Dave. I guess i'll just have to take the word of the ScanMaster and the DataMaster readings. you're right about not meeting the criteria for setting a code 21. That's why I'm so short now . I just shipped the chip off to Eric to analyze.

Damn, I swapped the ECU to the Sy (it set a bunch code 21's), but too short sighted to run the Sy box in the Ty. Hmmmm, that's why you're the expert in all SyTy related stuff:tup:

 

[Eric Sy GN]

Re: TPS Mystery

Just to help clarify, since this chip is not based on the stock 58 code (or 59), it uses different qualifications for a code 21 (TPS High).
In this case, it must see TPS over ~1.10v, and calculated airflow under 25 gr/sec, for 10 seconds. It would be difficult to achieve those conditions (I've never seen it), however maybe you've stumbled across those conditions and we need to tweak the settings a little. Now that I think about it, I could see it happening if you had a TPS sensor that is already on the high side at idle, like .90v or so.
When I get your chip, I'll move the voltage threshold up to something like 2.5 volts and lets see if that fixes it. In fact I plan to increase that value from now on just to avoid issues.
Regards,
Eric