A/F Gauge Stops Working- CEL On

[Knockin1g]

After normal driving in my 97 GST, suddenly my A/F gauge stops working and just stays on "rich" and my CE light comes on. No problem I thought and just changed the o2 sensor with a brand new one. After reseting the ECU the CEL still came back on and A/F gauge still does not cycle. What else could be causing this? Thanks for your advice.

 

[Nofear20]

You should get the CEL checked with a logger

 

[Knockin1g]

Yeah, I'm aware of that but I have no access to one.

 

[absolute_DSM]

Flash the codes.

http://www.dsmtuners.com/forums/newbie-forum/196421-1g-cel-codes.html

Diagnosis Port Error Codes

 

[Knockin1g]

I appreciate the link but I need it for a 2g I just did a search here on tuners and on vfaq but couldn't seem to find it yet.

 

[Boost92awd]

What year 2G? Depending on what year it is you could just take it to autozone and have them check it for you.

 

[Knockin1g]

Yeah I actually just read that in another topic, I got a 97, I'm about to call them and see if they can check it. Thanks!

 

[Boost92awd]

Yeah I actually just read that in another topic, I got a 97, I'm about to call them and see if they can check it. Thanks!

Yes they can check it, its OBDII. The check engine light has to be on though in order for them to read it.

 

[Knockin1g]

Ok so, I just went to Autozone and used their OBD II diagnostic device and my ECU read two check engine codes:

One for the oxygen sensor electrical circuit and another for coolant temp.

Autozone gave me two troubleshoot receipts that explained more about the CE codes it read which said-

"The PCM has determined that a malfunction exists in the electrical circuit for the O2 sensor-

Probable causes:

1. O2 sensor defective (not likely because I just replaced with a brand new one)
2. Fuel system running very rich or lean- repair other codes first
3. Engine misfire condition (not likely, my engine is not misfiring)
4. Fuel pressure very high or low- fuel pump or pressure regulator"

"The PCM has determined that the amount of time it took for the coolant temperature sensor to reach an input value consistent with closed loop operation was too excessive. Coolant temp always low-

Probable causes:

1. Check coolant level
2. Thermostat defective (not likely, changed recently, car warms up quickly, doesn't overheat)
3. ECT- Engine Coolant Temperature, sensor defective"

In addition, the car still drives good. I'm getting about 24mpg. I recently changed the spark plugs to some BPR6's but the old ones were still in good shape.

Any more advice on what I should troubleshoot next based on the above info?
Please help, thanks.

 

[Aftershock13]

I had a similar issue and it ended up being my MAF, do you have another one your could try?

I'm in the dark about the coolant issue . . . . . . but if there is a failure bad enough to throw a code alot of the times it's the sensor.

If you know someone that owns/works at a shop I would see if you can run a smog test and look at your co2/HC. Some of the gen 2's have 2 O2 sensors (like mine) and if your CAT is starting to go bad you'll throw a O2 code from the sensor right after the CAT. Let me know what you find.

 

[starsthensun]

I just had the same exact problem. Take off your interior panels to access your ECU. Look at the wire harness to the ECU and make sure that the wires for the a/f gauge and ECU wire harness are still connected. Sounds like your o2 sensor wire came loose. I bet that whoever installed your a/f gauge didn't soldier the wires and they vibrated loose. Here is a link for a 2g pinout to the ECU.


Jumptronix Installation Instructions

Also, go to www.vfaq.com for the proper installation of the a/f gauge ( Once on the vfaq's page go to electrical, and click on ecu pinouts for 2g turbos)

It should be pretty obvious where they tapped the wires in though. Just double check to make sure those three wires are still connected. Let us know what you find.

 

[Knockin1g]

Yep I checked it out the other day and that's exactly what happened. O2 Sensor signal wire came loose.
After I connected it back, CEL went away but A/F gauge still stuck on rich. I'm assuming car is stuck on "warm up mode" according to the other error code saying my car was running too cold.

 

[spyderturbo007]

Sounds like you might need a coolant temp sensor. Is the CEL still off, or did just the O2 sensor code go away?

When the sensor dies, it reports a value of -40 degrees to the ECU. That causes you to never reach closed loop operation. If I remember correctly, I paid about $26 from the dealer for the sensor. Just remember, there are 2 different sensors, one for the guage and one for the ECU. You want to specify that you'll need the sensor for the ECU.

 

[starsthensun]

After you connected the wires back together, did you reset the ecu/clear the codes?

 

[Knockin1g]

After I reconnected the O2 signal wire I did not reset the ECU or clear any codes, the CEL went of (and is staying off) by itself.

I'm going to double check the wiring for the coolant temp sensor and that doesn't solve anything then I guess I'll go get a new one. The coolant sensor off the waterneck that sends a signal to the ECU has a singe wire correct?

I might as well double check the coolant temp sensor wire at the ECU (since this was the case with my o2) Do you know which pin it is?

Thanks for your help guys, much appreciated!

 

[spyderturbo007]

ECU Pinout #20 for the coolant temp sensor. Personally, I've never seen one that didn't trip the CEL with a bad sensor, but it's entirely possible.

 

[Knockin1g]

So I checked the wiring for the coolant temp sensor and there visually doesn't seem to be anything wrong with it.

I recently reset the ECU by unplugging my battery and nothing has changed.

CEL is still off.

BUT, my concern is my O2 sensor is still NOT cycling at all, anytime. On cold/warm starts A/F gauge reads at max rich, same scenario after car is warmed up and driven, A/F gauge stuck on rich. A/F still reads rich, on/off throttle, on/off boost/vacuum.

Are the above symptoms realistic results of error code PO125- Insufficient Coolant Temperature to enter Closed Loop? Just a reminder, the OBDII scanner at Autozone picked up that ^^ code along with PO130( o2 sensor ciruit) before I reconnected the O2 sensor signal wire at the ECU.

So does all this mean I'm always in open-loop operation? Aside from a waste of fuel and poor economy are there any other detrimental effects from my cars condition?

This is my daily driver so I've been forced to drive the car in this condition for about a month or so already.

Spyderturbo007- Thanks for the replies and advice but I believe some people on this thread are getting confused as to which DSM I'm referring to. This thread is about my 97' GST not my 1g that's listed in my profile. 1g was sold and I gotta update my profile.

Thanks for the help!

 

[spyderturbo007]

Are the above symptoms realistic results of error code PO125- Insufficient Coolant Temperature to enter Closed Loop? Just a reminder, the OBDII scanner at Autozone picked up that ^^ code along with PO130( o2 sensor ciruit) before I reconnected the O2 sensor signal wire at the ECU.

Yes they are, but I've never seen one that didn't trip the CEL for the coolant temp sensor. Also, if you aren't tripping the CEL, then the ECU won't dump you in limp mode. There is something fishy going on here.

Does anyone have the conditions written down that the ECU requires before entering closed loop? I know I should have them memorized, but I don't.

So does all this mean I'm always in open-loop operation? Aside from a waste of fuel and poor economy are there any other detrimental effects from my cars condition?

Not open loop, but a really rich closed loop. If you had a logger, we could check to see if the FT's were moving. Are you sure there isn't something wrong with your O2 gauge? Can you probe the wire at the ECU with a volt meter just to be sure?