Check Engine Light/ O2

[Tank]

I have an Check Engine light that traces to the O2 sensors. But they're good. The problem seems to be with the ECU chip or the O2 wiring. Anyone know this problem and can you help?

Thanks

Tank

 

[donwon]

Did you recently do something to your car? i.e. headers, exhaust?

 

[Tank]

I did headers over a year ago. The O2 cable had to be extended and (gulp!) NSX Modified did an extention to that cable. I had a Check Engine light a while after that but it was a break in that cable. After that, over a year without a problem. Until now.

 

[Larry Bastanza]

May I ask how you confirmed the 02's are good? Did you swap with known good ones?

If so, check the male pins to see if one may be pushed in on each connector, also check the routing in case a wire may have burned.

What code do you get, heater code or mixture code??

HTH,
LarryB

 

[ak]

It could also be bad tank of gas? I'd say, check the cable first...make sure the connection for the extention is nicely soldered. If it's all good then get another tank of gas and reset the ECU. If it still persists then ask Larry B again

 

[Tank]

Did swap out sensors. Checked pins. Old extention cable was checked for burns (none found) but a new Comptech cable has arrived and will be installed to replace NSXM's homemade one.

It was a heater code.

Gas is new and good.

The car 'seems' to run fine. I have a race this weekend and all I need to do is basicly show up to get 3rd place for the season. But I have to actually show up. So I'll be there with the car even if I have to push it around the course.

Thanks for the input and please pass along any other suggestions.

Thanks again,

tt

 

[BryanZublin]

The heater in the O2 sensor is required to get the sensor up to operating temperature quickly for emissions reasons (after cold start). After the engine has been running for a few minutes under load, the O2 sensors will be hot enough from the exhaust gases and will output the correct voltage, and will not require any additional heat from the heater. So it is possible to have an error code for the heater (ie. open circuit) while the measured sensor output looks OK (rich > 0.45V, lean < 0.45V). The first O2 sensors on the market (1970's through early 1980's) were single wire type with no heater.

 

[Tank]

I have the Comptech extention cable on to the O2 sensors. It checks out electrically but my ECU is still showing a fault. It looks like that part of the chip got fried. Nothing else to do now but buy a new chip.

And when it rains, it pours. My power steering unit just went south. At least I can live without it.

 

[BryanZublin]

Originally posted by Tank I have the Comptech extention cable on to the O2 sensors. It checks out electrically but my ECU is still showing a fault. It looks like that part of the chip got fried. Nothing else to do now but buy a new chip.

Tank, if there was a problem with the chip in the ECU, the ECU would not even work and it would revert to "limp home" mode (indicated by 4000 RPM rev limit). I guarantee that chip (program memory) in your ECU is OK if you are not in limp home mode.

 

[Tank]

BZ, If the sensors are good and the wiring is good, what else could it be?

Thanks for the input,

t

 

[Larry Bastanza]

Do you have a digitial volt meter? Are you sure you have checked each wire electrically. The heater curcuit is pretty basic. It's just like a lightbulb at the end of two wires. You should check the resistance at the two wire connector that plug into the wiring harness on the way to the ECU. or better yet AT the ECU.

The online service manual has a test procedure on page 11-30. I have to agree with Bryan about the ECU, pretty unlikely.

HTH,
LarryB

 

[BryanZublin]

I would perform the procedure in the manual for checking the heater operation and O2 sensor feedback operatin. When the O2 sensor is working correctly and the ECU is in closed loop mode, the voltage from the O2 sensor will toggle between about 0.1V and 0.9V a few times per second. If you stab the throttle, the engine will go rich for a few seconds and the O2 sensor should read close to 0.9V. After you let off the throttle, it will go lean for a few seconds and will read about 0.1V or less.

It is still possible that there is a problem with the ECU, but not the program chip. There are signal conditioning circuits between all sensors and the ECU processor itself. There could be a failure in that part of the circuit.

 

[Tank]

Not to make a pun out of it but, those are some good leads. I'll let you know what I find out.

Thanks,

t