Help with TC fuse short term fix for bad tps

[RichM]

Hi guys

Long story but my NSX was at a local (now closed) tuner while getting a custom SPEC duel clutch built and a new AEM fuel management system with throttle body from SOS installed and tuned.

Unfortunately after 9 months got the car back from SPEC but non of the work other than clutch was done (I prepaid In full)

The car was loosing power once boost hit - TC LIGHT and CEL would come on- and based on the codes and past experience it was a TPS (I had one replaced years ago and it was a used one out of another Honda) this also happened yesterday after getting the car back.

Now I am Back to square one (less 10k) I still think it’s the TPS sensor and would like to take a couple of runs with the TC out of the picture by pulling the fuse (I have a 97) I can Not locate the fuse which I read Is in the engine bay - any help would be appreciated

Thanks

Rich

 

[Old Guy]

Short answer, there is no single fuse that can be removed to disable the TCS without disabling a bunch of other important stuff. Since you have a 1997, just push the TCS button on the dash to disable it.

If the TCS light in the cluster is permanenetly lit up it means one of two things. Either you have already turned off the TCS with the dash button or there is a problem with the TCS. If there is a problem with the TCS the TCS will disable itself. Either way, if the TCS light is on the TCS is out of the picture and is not the cause of your problems. Use the SC connector to determine if there are stored error codes in the TCS which may give you some clue as to what is going on.

If the CEL is coming on, use the SC to retrieve the CEL code or an OBDII code reader (assuming you are still running on the OEM ECU) to retrieve the error codes. The OBDII error codes will give you a clue as to what is going on and will indicate if the TPS is out of range. The TPS has a very minor function in engine operation and is unlikely to be the cause of significant operational problems (unless you are referring to one of the sensors that are part of the DBW feedback system).

If your AEM was never installed and you are trying to run a turbocharged engine on the OEM ECU (I assume that is how you get the CEL to light up?) you are in for a world of hurt. Once you enter the land of boost with an unmodified OEM ECU you have effectively fallen off the edge of the earth. If the AEM was installed on your turbo car; but, never tuned you are also in for a world of hurt.

 

[docjohn]

So sorry to see you and your car get screwed..did covid kill your shop..

 

[RichM]

Covid was blamed but they had other issues!

 

[RichM]

Thanks - I had come to that conclusion. My car was tuned with the AEM piggy back well before this mess. I have Had a bad TPS sensor (according to pulled codes) in the past and My the. Tuner replaced It with a Honda part (used) that fit - it ran fine for almost ten years (with the turbo) but last year under boost it would stutter , the TC light and CEL would come on - interestingly the ac would cut in and out (which makes me now think a ground may be the problem ) I did Disable TC yesterday after reading several threads and pulled full boost through 8k in several gears - ran for about 20 mins and then got fuel cut (or what felt like fuel cut ) and CEL drove her back without hitting boost and she was fine / idle perfect.

I am Thinking TPS sensor / wheel sensor (Although not indicated by cel codes) possibly ground (given the acc power cutting out)

Rich

 

[Old Guy]

The AEM piggy-back controller explains much.

The OEM ECU has a fail safe mode for certain sensors and I believe that the TPS is one of those. The service manual does not provide much detail about how it responds to a detected failure for the TPS. If it goes into a full limp mode that will result in a significant power reduction. However, my take away from the service manual is that once you enter the limp mode you stay in the limp mode. If the original problem happened to be intermittent and went away I don't think the limp mode goes away until you reset the ECU. But, I don't know that for sure because the service manual is not super detailed on that particular feature. So, you could be getting a limp mode problem; but, anything that would cause limp mode should set an OBDII code. If after your latest CEL incident you find that you have a code for the TPS then check the TPS. However, rather than just replace the TPS, do the test set out in the service manual.

When you say the AC would cut in and out, do you mean the climate control unit in the dash is doing something odd or do you mean that the clutch on the compressor is cutting in and out? If you mean that the clutch is cutting in and out, the clutch is controlled by the ECU. At high engine output the ECU shuts off the compressor to make more power available. If the clutch is being cycled by the ECU, it could be a sign that it is getting an intermittent signal from the TPS or MAP sensor about how wide open the throttle is. This intermittent signal might be caused by an intermittent wiring short on the TPS wiring rather than an actual TPS switch problem. To complicate things, the TPS shares a sanctioned +5v supply and ground with the MAP sensor and other critical devices. If you get a good ground in the TPS or the shared wiring the problem will ripple through to those other devices creating all kinds of potentially odd problems. As a matter of interest, does the piggy back have a MAP sensor and provides a modified MAP signal back to the ECU or does it rely on the OEM MAP? If the MAP sensor is part of the AEM system you might want to look at that to see if the problem is originating there.

So, I suggest that you read the error codes first. If you are getting a TPS error code, then do the tests set out in the service manual for the TPS rather than do an immediate replacement. If the TPS fails the tests, then replace. I believe that the TPS from a 1998 - 2000 Civic, also used by a bunch of other Honda products is a replacement. If the TPS appears to be OK, then carefully check the wiring to the TPS. Some of this wiring is shared with the MAP and EGR lift sensors so lots of places to check for damaged wiring.

I doubt that you have a wheel speed sensor problem. Wheel speed sensors are dumb-ass reliable reluctance sensors and tend to work just fine up to the point that they get taken out by a piece of garbage hitting them or the wire breaks near the entry point to the sensor. They either read wheel speed accurately or not at all. They don't read low or high or odd speeds. If a sensor has failed the TCS controller should detect that, set a code and disable itself. If the TCS does not have any error codes then don't put effort into messing with the wheel speed sensors. There are lots of other places to look for your problem first. You can go back to checking the TCS if you can't find the problem in the likely spots.

 

[RichM]

Thanks for the additional help.

I continue to get a 1243 code - funny thing is that when I search This code on the forum I see my own thread from 2009 when I had The same problem! (But for the power cutting on and off on the climate control -display cuts in an out - not the clutch )

Back then we switched out the tps for a used Honda part and it’s been fine until now. I do Not get an ABS error so speed sensor is probably not an issue. I use The stock map sensor.

Turning off the TC does seem to mainly fix problem but the climate control adds a new dimension - I have seen a couple of threads that mentions this issue - in one case there was a ground issue, the other was a loose fuse (33 I think)

I will Experiment with driving with the tc off and run a diagnostic on the tps

Thanks

Rich

 

[Old Guy]

1243 is a TPS trouble code; but, it appears to be a trouble code associated with the drive by wire system rather than the fuel control system. P0122 and P0123 are the traditional non Honda specific codes associated with the TPS. Do they show up? If not, that would suggest the problem is associated with the DBW. Certain errors (Honda does not specify) will cause the DBW to go into fail safe mode which results in the DBW restricting operation (Honda also does not specify what that means). That might be what you experience.

The DBW part of the ECU monitors the accelerator pedal position and the throttle position. I am just speculating; but, if the DBW / ECU detects a conflict between the two it presumably generates an error code and may enter fail safe mode. Code 1243 says insufficient position so perhaps the ECM is reading the accelerator position sensors and not getting a matching opening from the TPS. You obviously have a scanner to pull codes. Is it capable of reading variables such as TPS? If so, use it to check the TPS position. The service manual specifies that the TPS should vary from 10% closed to 90% wide open when read by the scan tool. If you get those readings, then your TPS is probably OK (at this particular time). If the numbers are off you might have a positioning problem with the TPS. If the numbers do not change smoothly then you likely have a worn TPS. Faulty wiring that results in intermittent or high resistance shorts could mimic a failing TPS. Perhaps when your throttle body was modified the TPS position got messed up.

As you note, the climate control gets power from fuse #33 which is the 'clock' fuse which doubles as the keep alive power for the ECU, TCS EPS……. Loss of power on fuse #33 might erase codes; but, aside from the CCU going dead its not obvious that a problem on that circuit would cause your driveability problems.

 

[RichM]

Thanks old guy

I will Get a voltmeter on the tps as my scan tool can not read this -

It may be that I am Looking for one fix for a compound problem - but I will Focus on the drivability first.

Also checking connections in my boom slang to my aem unit

Ps the throttle body is stock as the “tuner” took my money for the stand alone SOS aem unit with throttle body but never ordered it

Rich

 

[RichM]

Looks like its the TPS

new code reader tells me I'm getting from 9 to 50% - once the CEL comes on it drops to 38%

also my Climate Control unit continues to turn on an off randomly (although sometimes if I rev the engine it flickers back to life) the self check works sometimes sometimes nothing. I think it may be a low battery is to blame so i will switch out the battery and see.

Rich

 

[Old Guy]

Looks like its the TPS

new code reader tells me I'm getting from 9 to 50% - once the CEL comes on it drops to 38%

also my Climate Control unit continues to turn on an off randomly (although sometimes if I rev the engine it flickers back to life) the self check works sometimes sometimes nothing. I think it may be a low battery is to blame so i will switch out the battery and see.

Rich

If the code reader says that the TPS position only goes from 9% to 50% when you do pedal to the floor, that would be a significant problem. Seems like its time for a new TPS. This time go new rather than used. I think sensors from a 2000 ish Civic are a direct fit. You are on your own for the adjustment procedure as the service manual treats this as a non maintainable item.

Your battery may or may not be getting old; but, if the climate control display is actually blinking on and off when the car is running the battery is likely the last suspect. Once the engine is running the alternator is doing all the heavy lifting in terms of voltage control and supplying load (perhaps with the exception of the EPS). With some minor fiddling, once the engine is running cars with good sized alternators will run OK with the battery disconnected. If the CCU is blinking on and off you have an electrical supply problem some place - this could include a problem with the connections to the CCU or damage on the CCU board itself.

 

[RichM]

Thanks- makes sense

The CCU has had the typical issue of only working on High so i will send it out to have the board looked at.

I ordered a new TPS from BLOX - should have it in next week

Rich

 

[Old Guy]

Thanks- makes sense

The CCU has had the typical issue of only working on High so i will send it out to have the board looked at.

I ordered a new TPS from BLOX - should have it in next week

Rich

CCU only working on high - do you mean that the fan speed only works on high? If so, and it always operates only on high speed, that can be a sign that the power transistor for the blower control has failed. New non OEM replacement modules are available for about $200. If you are so inclined, its messy; but, you can dig the power transistor out of its housing and replace it for less than $20. The CCU can also cause the only on high speed problem; but, if the CCU passes its self tests the problem may be with the transistor although they tend to be seriously reliable devices.

 

[RichM]

I ran the self test on the CCU - when the power is on it cycles through all the modes but the fan only operates at high speed

The CCU has only worked on high for a year - was waiting to upgrade stereo to fix it - but it always worked

The power cut problem just showed up when the TPS problem started - that’s why I was Looking (incorrectly) to tie them together !