NOTE: This is actually a post from the Road Racing / Autocross & Time Attack section of this forum. They suggested I also post here for more car-specific info. Check out my previous post for more information: https://honda-tech.com/forums/road-r...-mode-3337180/

We have a 2002 Civic EX with a 1.7L VTEC motor in it. I believe it is a B17A2. The car is raced on asphalt circle track, so it has some modifications.
Every race we go to, the car seems to enter a "limp mode" (2000-3000rpms) after around 5 minutes (5-8 laps) on the track. Some people around the track seem to think it is the car entering VTEC Limp mode.

We have GoPro footage of the problem occuring - pay close attention to the drivers foot. The car becomes completely unresponsive. (car dies around 9:00 - the forum removes my link with the time)


After asking people around the track, they tell us just to get rid of VTEC! There has to be a solution to this problem.

### Things about the car

- It's lacking it's entire interior (including dash - we've been told VTEC might care about the factory dash?)

- Battery has been relocated

- Engine bay fuse box has been relocated

- Several Sensors have been deleted. From the top of my head, I know the downstream 02 and water temp gauge sensor (though the ECU still gets a water temp). It is the one in the thermostat housing

- Inline Fuel shutoff (possible fuel restriction, though unlikely - it runs good when it runs)

- We use a Bluetooth ODB2 sensor to record data on a phone. The app is somewhat meh, and only records some data, but we have data to look back on.

### Things we know

- Car seems to drop to 2000-3000rpms after ~5minutes (5-8 laps) on the track
- The car was kept out after it died once, and it died a second time around 2 laps later

- Always does it, never works for more than 8 laps

- Didn't always do it - here is a video of me driving the car the week before this started happening at practice for 9 laps -
- The car previously had a bad camshaft sensor, causing it to rev limit at 4500rpm.

- ECU is throwing 3 Check Engine Codes:
- P0141: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) – Downstream
- P0131: O2 Sensor Signal Low Voltage (Bank 1, Sensor 1)
- P0132: 02 Sensor Circuit High Voltage (Bank 1 Sensor 1)
- I believe it threw an Injector Driver Module code previously, when it had a bad camshaft sensor

- OpenLoop (OL) fault on Fuel System 1

- In one log, we saw a temp spike to 300F *around* the time the car gave out. This wasn't exact, and it hasn't happened again that we've seen.

### Things we've tried

- Thicker oil - 20w50
- We've been told that the oil can sling to the right of the motor, not be picked up, and cause fluxuations in oil pressure.
Vtec will drop out if there is not enough oil pressure. Heavier oil didn't seem to make a difference.

- Jumping VTEC Oil Pressure sensor to VTEC solenoid via toggle switch
- You can see this in the video - it's the switch on the right

----------------------

I suspect our problem is related to something reaching a certain temperature (whether that be overheating, or reaching operating temp and realizing other systems are failing).
We've been told that numerous systems need to be active and working allow VTEC to work correctly, though we can't find a definitive list of what needs to exist for VTEC.


Questions I have:

- Does this sound like it could be caused by VTEC?

- What sensors/systems need to be working properly for VTEC to function?

- What could put the car into limp-mode like this?

 

Try another pcm. You can get one with the matching chip key off ebay.
https://www.ebay.com/i/123660353161?chn=ps
That may do the trick but I can't say it will for sure.

 

Buying another ECU is kind of a last resort for us. I don't think that's it's bad, I think it's missing something for VTEC and panicking as it should.

I've read lots of places that the ECU needs to see Water Temp, Oil Pressure, and VSS for VTEC to operate correctly. Does anyone know the actual values? 180F or 200F for water temp? What oil pressure? I've read about 20mph for VSS, that one I'm sure we've achieved.

Does anyone even have a stock Tune I can open in TunerPro to dig around for those values myself? I tried finding somewhere I can download the ECU files, but all my resources are GM oriented.

 

So you state you removed the downstream O2 sensor, and its throwing codes for downstream O2 failure. The stock ECU uses the downstream O2 sensor to manage fuel ratios actively, and if you don't have one... its always going to throw a code. Is this due to the fact that you're not running a catalytic converter? If so, mount the downstream sensor on a J-pipe extension or use some spark plug defoulers to space it out and limit its exposure to exhaust gases.

D17's are also extremely prone to warped heads and blown headgaskets, so if you overheated it that badly (300 deg), its possible that you may need to pull the head.

 

The downstream code is expected. I realize the AF ratio might be off without it, however, that shouldn't cause the car to cut ignition, should it? You are correct that it is because of the lack of a cat converter. We got the car with nothing more than the manifold and downpipe. We can add one back, but is that going to fix the car shutting off? I don't suspect so, and we can't afford to throw money at the problem to replace all the sensors

To clarify: the car did NOT reach 300f. The temp sensor spiked to that in one of our 3 data logs. It did not remain that temp, and We did not see a spike of that magnitude again.

We are going to the track tomorrow to test a couple things to better diagnose the problem.

 

You didn't say "cut the ignition" in the title, so I assumed it was just going into LIMP mode. If the car is only going into a LIMP mode after 5 minutes of operation, it would lead me to believe that the car has gone through its warmup grace period and is leaving Closed Loop operation for Open Loop. This would mean the ECU would start polling data from the secondary O2 sensor actively, instead of running a standard Closed Loop fuel map. If it doesn't get data from that secondary O2 sensor, it would lead me to believe that the car would throw a code for it and run only in LIMP mode.

 

Interesting. It's too late to add one now, but I'll keep this in mind at the track tomorrow. Will let you know how it goes.

Thanks for the info!

 

Downstream O2 will throw a code for slow to warm up or not functioning. The car doesn't use the input from the downstream O2 to run the engine however, nor will it go into limp mode because of a downstream O2 issue.

 

Thanks for the info, this is what I would have expected.

 

Sorry for the late update - here's what happened.

We took it up to the track on Memorial day. I drive the car for around ~20 laps. This is what happened:

8 laps - Car enters limp mode around 160gauge/200 ECU. Car stays in limp mode for around 30 seconds. Car has a hard cut off at 3000rpms (not 2000 as previously mentioned).

At this point, I stayed on the track to cause the condition again.

3 laps later - Car Enters limp mode again. Engine is slightly warmer. This time, I shift to neutral and let the car idle down, and the car only stays in limp mode for ~10 seconds. (Maybe exists limp mode once it hits a certain RPM?)

~8 laps later - Car enters limp mode a final time, and I enter the pits. Car reads a final temp of 190gauge/240 ECU. (Removes my suspicion it is _only_ at 200 ECU that the issue occurs.)

If there is interest, I can get the video of this run onto youtube.

Someone suggested getting a second water temp sensor and leaving it in the engine bay. The theory here was to never allow the car to think that it is warmed up enough for limp mode. This worked for about 11 laps, until the driver (not me this time) blew a tire and we didn't have a spare.

We had enough confidence in our "band-aid" to take it to the track last Saturday. The car completed the day fine, never entering limp mode with the engine temp sensor in the engine bay.

On another note, we currently are not getting any readings from the ECU for speed. Though the car does not have a stock dash, I would expect to still get a reading - we are going to replace the VSS sensor on the transmission and see if we can get the car into VTEC during hotlaps.


TLDR; We put the water temp sensor in the engine bay and tricked the ECU into never entering limp mode because it never tries to activate VTEC. We would still eventually like to solve real problem, but atleast now the car is raceable. Going to try a VSS sensor ASAP (it's in the mail).