1G I can't get rid of this check engine light

[greyspyder117]

I have tried everything and i thought i was finally rid of this darn check engine light in my 1ga GSX.

It comes up as a ECT code and i took apart the car today and tried to fix it. I disconnected the clip and did the ohm test it was no good. So i went and got a new sensor. While the sensor was out i checked the voltage at the wires and it came up 4.7v. So even with the right volts and new sensor i am still throwing a code what do i do now.

The ECT makes the car go into closed loop so i am stuck in open loop all the time and dumping gas.

Anyone have any ideas.

 

[gofer]

I have tried everything and i thought i was finally rid of this darn check engine light in my 1ga GSX. It comes up as a ECT code and i took apart the car today and tried to fix it. I disconnected the clip and did the ohm test it was no good. So i went and got a new sensor. While the sensor was out i checked the voltage at the wires and it came up 4.7v. So even with the right volts and new sensor i am still throwing a code what do i do now. The ECT makes the car go into closed loop so i am stuck in open loop all the time and dumping gas. Anyone have any ideas.

Whats your o2 sensor doing?

 

[greyspyder117]

Well i think i know what you mean by that but... What do you mean whats it doing?

 

[DSM1G90]

sounds like something else is in the "open loop" condition. Mine basically did the same and it was a toasted ground trace on the ECU momboard that had opened up.

 

[gofer]

Well i think i know what you mean by that but... What do you ,ean whats it doing

In closed loop operation the ECU "watches" the front o2 sensor for feedback voltages to keep your AFR's at 14.7:1 or Stoich. Your front o2 sensor is a narrowband (0-1V) sensor so it should cycle showing the ECU rich/lean values (.1 to .8V) during closed loop. If your front o2 sensor isn't cycling the ECU has nothing to look at to control closed loop fuel trims, therefore locking it in open loop.

Basically what all thats saying is if your front o2 sensor is bad your car will be locked in open loop too.

 

[delta448]

Back probe the wiring harnesses for a continuity test from coolant temp sensor output to ECU pin 20.

1G Turbo ECU pinouts

edit: sorry for anyone who saw before I corrected, I saw 97 GST Spyder under the username before re-reading 1Ga.

 

[greyspyder117]

In closed loop operation the ECU "watches" the front o2 sensor for feedback voltages to keep your AFR's at 14.7:1 or Stoich. Your front o2 sensor is a narrowband (0-1V) sensor so it should cycle showing the ECU rich/lean values (.1 to .8V) during closed loop. If your front o2 sensor isn't cycling the ECU has nothing to look at to control closed loop fuel trims, therefore locking it in open loop.

Basically what all thats saying is if your front o2 sensor is bad your car will be locked in open loop too.

OK i now read how to test o2 function in the manual but i am still throwing a ect code my bad o2 would throw a ect code?

 

[gofer]

What sensor did you replace, the 2 wire ECU ect sensor or the 1 wire gauge ect sensor?

 

[greyspyder117]

2 wire is the one i replaced the one wire is for the gauge i believe....

 

[gofer]

Yep, I was just making sure you replaced the correct sensor because the 1 wire is for the gauge and wouldn't get rid of the CEL.

Those wires can rot after 19 to 20 yrs of DD'ing coming off the back of the waterneck like that. Before you keep replacing stuff and throwing money into it I would start chasing wires. Especially check their connections going to the back of the sensor.

 

[DSM1G90]

I saw 97 GST Spyder under the username before re-reading 1Ga

Don't worry on that for his beginning descript was a "1Ga GSX" - Then, he's suddenly switched gears to the '97 GST Spyder .. which is a "2Gb" vehicle.

So, what is it?

 

[nyTalonTsi]

Lol hes referring to his 91 GSX that has this problem.

 

[greyspyder117]

Don't worry on that for his beginning descript was a "1Ga GSX" - Then, he's suddenly switched gears to the '97 GST Spyder .. which is a "2Gb" vehicle.

So, what is it?

I never switched gears to the spyder. The spyder is what i had first i then bought the 91 GSX. The question was clearly stated for the 91 GSX if you read the post . Am i not allowed to own both? This was the most helpful thread i have gotten in a few months on here with no bulshit. There really good answers from the other guys please don't ruin it with your bullshit. Your the type of guy i hate to run into on here and there are alot of you. Did i misspell anything anywhere?? What about my grammer?? Listen you don't have a answer to my problem please don't post in my thread. I am trying to figure this out not get hounded for stupid shit thank you...

 

[delta448]

Back probe the wiring harnesses for a continuity test from coolant temp sensor output to ECU pin 20.

If this checks out, your next step is to check the sensor output for continuity against ground (and also make sure the sensor grounding has a low resistance to the main battery chassis ground connection).

I just think if you're seeing good voltage to the sensor, know the sensor is good and still have the CEL for it, then the old wiring or a bad ECU trace is most likely to be the problem.

Just for sh--s and giggles, you might consider also checking the coolant level. If the sensor is hanging in air, it reacts much slower to temperature changes.

 

[jrohner]

There is actually another ECT sensor, something to do with the air conditioning, make sure it wasn't that one you replaced instead of the one going to the ECU. Do you have access to a logger so you can check the ECT in the ECU?