95' gs CEL mystery

[midniteblack]

ok, first of all i own a 95' gs eclipse. 157k, manual tranny. i have had a check engine light since i bought the car. There are two codes, P0422: Catalytic Converter efficiency failure (m/t) & P1391: Intermittent loss of CMP or CKP sensors. here's the thing, i'm going to try to fix these codes but i have a wierd issue with my CEL that isn't relevant to the codes. If i completely top off my gas tank i'll hop in the car and the CEL will be gone. I'll drive for about 15-30 miles and it will come back on. Then as my tank is about almost empty the light will go away again. Whacked out ECU maybe? any help is appreciated! thanks.

9/15/09 Edit: I have replaced my Crank Sensor. Took off my Cat and checked it out and the cat looked to be in good condition. I still have this dreaded CEL with the same codes and on occasion my car will stutter like there is a fuel cut or something. Should i take apart the ecu to look to see how it looks?

 

[96TurboGS]

Weird, you usually should see that kind of code being EVAP related. If you have your EGR still connected make sure the wires in the harness hasn’t melted into another. Just because the CEL goes off doesn’t mean the ecu cleared the codes from its memory (if it does, change the ecu or look into your wiring). With 150k+ you might want to look into changing the CC if you haven’t already, but first check for exhaust leaks and it glowing at night. As for the P1391 check wire connections to the PCM, and make sure the oil seal around both sensors aren’t damaged and there’s no oil in the connectors. Sounds like an electric problem somewhere rather then the sensors itself. Does the car start up and drive ok?

 

[95GsTreez]

That is wierd. I dont think the light going out is related to your CEL. Just fix them. The light goes of when it verifies that the problem is gone after a set number of drive cycles. Same thing for when it comes on. And if he has the p0422 code the CEL should be blinking...thats wierd too. Is it blinking?

 

[midniteblack]

the car starts and drives fine. my tech book says that if the sensors were to fail the car will still drive fine because the ecu will just run off of the last memory it had before the sensors went out. This might explain why my car seems like its running rich. the CEL is not blinking either.

 

[rstare]

You won't have spark without the Crank or Cam position sensor.
'95's are known to have some problems with the ECU's failing.

 

[midniteblack]

You won't have spark without the Crank or Cam position sensor.
'95's are known to have some problems with the ECU's failing.

well the code states that it's intermittent loss of one of these sensors. also, i've read my car will run perfectly fine if one of these sensors fail. it will run off of the last memory of the ecu. I have also read 95's are prone to having ECU failures. I think that may be one of the problems. it just makes no sence that the CEL light turns on and off with the levels of gas in my tank.

 

[2point3Tsi]

cat efficiency codes can also be related to rear o2 sensors if it thinks its working right. o2 sensors will usually only trigger a heater circuit failure for codes. If you have a good multi-meter that refreshes fast you can watch the voltage of your rear o2 to cycle up and down, if gets stuck it could be it

 

[rstare]

i've read my car will run perfectly fine if one of these sensors fail. it will run off of the last memory of the ecu.

I'm not just speaking for the hell of it; you will NOT have spark without that sensor. How can it go off the last memory? The RPM's differ constantley.
In one of the crank counterweights there is teeth etched into it. When the metal portions align with the sensor the voltage spikes and the ecu uses these spikes along with a 60* timing notch to determine engine speed.
If the ecu is getting a wrong signal, or no signal it can't determine engine speed and cannot fire spark correctly.

 

[midniteblack]

I'm not just speaking for the hell of it; you will NOT have spark without that sensor. How can it go off the last memory? The RPM's differ constantley.
In one of the crank counterweights there is teeth etched into it. When the metal portions align with the sensor the voltage spikes and the ecu uses these spikes along with a 60* timing notch to determine engine speed.
If the ecu is getting a wrong signal, or no signal it can't determine engine speed and cannot fire spark correctly.

i'm sorry, what i stated was about a failed o2 sensor. i do know that if the cam signal gets lost, the fuel injection system will shift to a calculated mode based on the last fuel injection pulse and continue to run.

 

[rstare]

i'm sorry, what i stated was about a failed o2 sensor. i do know that if the cam signal gets lost, the fuel injection system will shift to a calculated mode based on the last fuel injection pulse and continue to run.

Yes, a failed 02 sensor will cause the ecu to remain in open loop. The ecu will use the fuel trim in it's memory.
The CPS however is also used for spark, agian if it fails you will have incorrect or no input and the ecu will not fire spark correctly. There seems to be lots of disagreements on whether or not the CPS is needed for the car to run; I have heard alot of people argue both ways. But I know for certain my car will NOT run without the CPS, I tried.

 

[midniteblack]

bump...

 

[VelocitàPaola]

There seems to be lots of disagreements on whether or not the CPS is needed for the car to run; I have heard alot of people argue both ways. But I know for certain my car will NOT run without the CPS, I tried.

Yeah, it's got to be another one of those differences between model years. I know for a fact that my car will run without the CPS. I can imagine engineers not having put such a safeguard in the older style ECU, but then doing so for the SBEC-III's.

 

[VelocitàPaola]

bump...

No.

Read the rules (again, since you were required to have read them to register in the first place):

DSM Forums - FAQ: Site Rules & Guidelines

 

[Fotowntalon]

I think he bumped becuase he edited it the same day. But yeah, most people are going to miss the edit with the update, it would be easier if you just updated in a new post with the information, that way people can more easily see it and help you out.

 

[midniteblack]

No.

Read the rules (again, since you were required to have read them to register in the first place):

DSM Forums - FAQ: Site Rules & Guidelines

sorry i used the word "bump", but i didn't just bump my thread without supplying some new information. I figured it would just be more convenient if i put the info at the top of the page. I suppose i won't next time.

 

[VelocitàPaola]

sorry i used the word "bump", but i didn't just bump my thread without supplying some new information. I figured it would just be more convenient if i put the info at the top of the page. I suppose i won't next time.

Just make a new post with your updated information next time. That way your thread goes to the top of the forum. Most people look at the bottom of a thread for new information, so doing what you did is unnecessary. It was a good idea, but misguided.