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Trying to help a friend out with his 1996 Geo metro with a 1.0 L, 5 speed car.
The car is setting a PO134 code, heated O2 sensor circuit insuffectient activity, sensor 1.
He has a scan tool or reader that can read live data, The front O2 sensor is reading from .7 to .9 volts almost all the time, sometimes while driving the reading my get down to .5 but never below it. The STFT is -20.3 at idle. The plugs look black like from a rich condition.
The fuel pressure was checked. The fuel pressure range is 13 to 20 psi at idle, he states he got 22 psi. While it is 2 psi over, I'm not sure how accurate his gauge is, or if the 2 psi could cause a 20% increase in fuel.
The EVAP vacuum line going to the intake manifold was disconnected to verify that the EVAP system was not allowing fuel in when it wasn't supppose to. The rich condition did not change with the vacuum line disconnected.
The front O2 and rear O2 sensors have been replaced. The fuel injector has been replaced.
The PCM has the DFCO function. While the engine is in DFCO, the STFT, front O2 signal and rear O2 signal all go to ZERO. That also means the fuel injector is not leaky or it would show up during DFCO.
What other suggestions, or things to check would you suggest.
DIYGUY wrote: One other thing I forgot to mention was the ECT and IAT reads correctly at ambient temps and does increase in temps as the engine warms up.
An incorrect ECT signal could cause a rich condition.
Disconnect the connectors. You should notice a change in the scanner Data PID's when you disconnect the connector. You should have a LESS than 100 mv on the sensor grounds (Lt Grn/Blk wires). With a volt meter, check the voltage on the signal wires, (Gray wire(IAT) and the Gray/white wire (ECT)).
Connect an incandescent test light to a good ground. While watching both the volt meter and the Data Pid's on the Scanner, touch the test light to the signal wires. The voltage should drop and the DATA PID should go from one extreme, to the other.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
DIYGUY wrote: One other thing I forgot to mention was the ECT and IAT reads correctly at ambient temps and does increase in temps as the engine warms up.
An incorrect ECT signal could cause a rich condition.
Disconnect the connectors. You should notice a change in the scanner Data PID's when you disconnect the connector. You should have a LESS than 100 mv on the sensor grounds (Lt Grn/Blk wires). With a volt meter, check the voltage on the signal wires, (Gray wire(IAT) and the Gray/white wire (ECT)).
Connect an incandescent test light to a good ground. While watching both the volt meter and the Data Pid's on the Scanner, touch the test light to the signal wires. The voltage should drop and the DATA PID should go from one extreme, to the other.
I'm impressed, do you use all data, or do you have a metro?
Your right checking the Lt Grn/ Black wire would check to make sure all grounds a good and not interfering with the sensors signals. I will have him check those and see what the results are.
We have not checked any signals wires yet, but can do that also.
DIYGUY wrote: I'm impressed, do you use all data, or do you have a metro?
For the wire colors, I use AllData.
The know-how came from paying attention to ScannerDanner.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
If you haven't, already, check out ScannerDanner Premium. You can sit in, from Day 1, as Paul teaches his class at Rosedale Tech. With a 14-day free trial, you have nothing to lose. And, if you want to learn, you will not regret it.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
pole71 wrote: If you haven't, already, check out ScannerDanner Premium. You can sit in, from Day 1, as Paul teaches his class at Rosedale Tech. With a 14-day free trial, you have nothing to lose. And, if you want to learn, you will not regriet it.
Unfortunately, I work everyday and don't think I could get enough videos watched to make it worth it.
Did you test the ECT circuit with the sensor disconnected. If the Circuit checks
"OK", but the temp reading doesn't change with engine temperature, then the Temp sensor is bad and is, likely, the input you are looking for.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
DIYGUY wrote: One other thing I forgot to mention was the ECT and IAT reads correctly at ambient temps and does increase in temps as the engine warms up.
My apologies. I just went back and Re-read that post. I mis-read it the first time. :blush: :oops: I thought you said It DOESN'T increase as the engine warms up.:dry:
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
DIYGUY wrote: One other thing I forgot to mention was the ECT and IAT reads correctly at ambient temps and does increase in temps as the engine warms up.
My apologies. I just went back and Re-read that post. I mis-read it the first time. :blush: :oops: I thought you said It DOESN'T increase as the engine warms up.:dry:
That's ok, no harm done.
I plan on tring to test the O2 sensor circuit and ground wire circuits early this week. Hopefully I will have some results to show.
My apologies. I just went back and Re-read that post. I mis-read it the first time. :blush: :oops: I thought you said It DOESN'T increase as the engine warms up.:dry: