Intermittant Code 44 (Left Oxy Sens Lean)
Thread Starter
7th Gear
Joined: Oct 2004
Posts: 7
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Oxygen Sensor Code Update
Since my last post I have been busy testing and collecting data. I thought I had it fixed at one point but the condition has returned. It seems to be in a failed state right now in the garage. The left O2 is reading 8 milivolts cold. The right side is reading 448 milivolts (ECM reference voltage) which seems correct. I have isolated the circuit by removing the pin connector from the ECM and the voltage did not change. I then measured the voltage at the ECM between the left O2 terminal and the ground terminal and confirmed that the ECM is not sending the correct reference voltage.
My problem is the ECM has already been replaced for this problem by the previous owner. The only other factor is that the car is cold and the manual states that these readings should be measured with the vehicle at oprerating temperature. I will drive the car today and see what happens.
My problem is the ECM has already been replaced for this problem by the previous owner. The only other factor is that the car is cold and the manual states that these readings should be measured with the vehicle at oprerating temperature. I will drive the car today and see what happens.
Thread Starter
7th Gear
Joined: Oct 2004
Posts: 7
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Test Drive Results
I drove the car today long enough to warm it up and the code 44 persists. All of the voltage readings I took when the car was cold are still the same. Everything points to the ECM. The only other thing to check is the main ground for the ECM but it is difficult to access. It's under the exhaust manifold, on the block above the oil filter. I think it's a long shot but I've been fooled by bad grounds before.
Any thoughts?
Any thoughts?
Thread Starter
7th Gear
Joined: Oct 2004
Posts: 7
Likes: 0
It was intermittant, but it's been in a "failed" state for a while now. I have been checking the codes and data with a scan tool that allows me to erase codes. I have pulled the pin connectors from the ECM harness connector and checked the fit. They all feel tight and look good. I have checked the one for the left O2 sensor and the O2 ground. The only terminal I could not get out was the one at the O2 sensor itself. But I didn't worry about that too much because my low voltage readings indicate a short to ground or a faulty ECM. The ECM sends a reference voltage of 450 milivolts to the sensor. With the O2 disconnected, that is what you should read and yet I get 8 milivolts when I disconnect it. I have checked the circuit and it is not grounded and shows continuity. The only thing that made me think of the main ECM ground is that maybe the ECM isn't operating properly as a result of a faulty ground. It's getting good voltage, so I can't think of anything else. It's just odd that everything else works fine and the car runs good. 
Le Mans Master
Joined: Jan 2003
Posts: 8,596
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From: Portland Oregon
Originally Posted by rlester2
It was intermittant, but it's been in a "failed" state for a while now. I have been checking the codes and data with a scan tool that allows me to erase codes. I have pulled the pin connectors from the ECM harness connector and checked the fit. They all feel tight and look good. I have checked the one for the left O2 sensor and the O2 ground. The only terminal I could not get out was the one at the O2 sensor itself. But I didn't worry about that too much because my low voltage readings indicate a short to ground or a faulty ECM. The ECM sends a reference voltage of 450 milivolts to the sensor. With the O2 disconnected, that is what you should read and yet I get 8 milivolts when I disconnect it. I have checked the circuit and it is not grounded and shows continuity. The only thing that made me think of the main ECM ground is that maybe the ECM isn't operating properly as a result of a faulty ground. It's getting good voltage, so I can't think of anything else. It's just odd that everything else works fine and the car runs good.
Thread Starter
7th Gear
Joined: Oct 2004
Posts: 7
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I think that is good advice. I will check the ECM ground by removing the bolt and I will clean the terminal ends.
I did check the circuit for resistance and got 0 ohms from one end to the other. When I checked for a ground I got infinate or open. (I am using a digital high impedence meter). The condition was present before and after the tests so I am sure the sircuit is OK. I inspected the harness and I couldn't see any problem areas. I did the usual moving around of the harness with the meter hooked up.
I'll let you know what happens with the ground terminal.
I did check the circuit for resistance and got 0 ohms from one end to the other. When I checked for a ground I got infinate or open. (I am using a digital high impedence meter). The condition was present before and after the tests so I am sure the sircuit is OK. I inspected the harness and I couldn't see any problem areas. I did the usual moving around of the harness with the meter hooked up.
I'll let you know what happens with the ground terminal.
