O2 Sensor Voltage

For the last few years I have been fighting constant problems with B1S1 O2 sensor. P0133. I replaced all four O2 sensors with new NTK and then replaced B1S1 again with new NTK. I learned to live with the MIL coming on and going off.

Recently I have started getting P0172 and P0300 with violent shaking. It seems all three of these codes could be connected to the O2 sensor so now I can't keep ignoring it.

I did a smoke test and there are no exhaust leaks.

Looking at the powertrain troubleshooting manual for P0133, test 3:

• Turn the ignition off
• Disconnect the O2 Sensor harness connector.
• Ignition on, engine not running.
• Measure the voltage on the O2 Signal circuit in the O2 Sensor harness connector.
• Is the voltage between 4.5 and 5.0 volts?
• Yes ! Go To 4
• No ! Check the O2 Signal circuit for damage, short to ground, open, or short to voltage. If OK, replace and program the Powertrain Control Module per Service Information.
• Perform POWERTRAIN VERIFICATION TEST VER - 5.

I did this and I get 3.95V on the signal circuit (K41) for B1S1 at the connector. I don't see any wiring damage.

Resistance between the ground in the B1S1 connector and the power steering pump body is 0.0 Ohms.

Resistance between the O2 sensor signal (K41) and ground is 570k.

Resistance between C2 (orange) pin 31 (K41) and the O2 sensor socket pin (K41) is 0.4 Ohms.

It seems according to the powertrain troubleshooting manual that the next step is to replace the PCM. Any other ideas?

I am going to work through the troubleshooting for the other codes, but it seems regardless the PCM is not right?

Thanks, Andy

B1Toad said:

Can you get a T pin and check K41 right at the PCM?

Click to expand...

With ignition on, the voltage on the K41 PCM pin is 3.3V and drops over about a minute to 2.2V.

Andy

With ignition on and fully warm, sensor 1/1 is toggling between 0.1V and 0.88V. 2/1 is toggling between 0.1V and 0.8V. However 1/2 is fairly static at 0.12V and 2/2 is fairly static at 0.61V to 0.76V. Seems strange that the two banks are giving different readings?

The O2S voltages are 1/1 is toggling between 2.59V and 3.37V, 1/2 is almost static at 2.6V and 2/2 is almost static at 3.26V. It seems DRB-III doesn't give an O2S voltage for 2/1.

I then turned the engine off and watch the O2S voltages as the sensors cooled down. 1/2 and 2/2 climbed to 4.97V but 1/1 climbed more slowly and I stopped the test when it had reached 4.44V.

I checked the bank one pre-cat with a borescope from the top and it looked OK.

Throttle position sensor is working fine.

Andy

I think the problem I have is transient - bank one goes into a strange state then back out of it again. Lots of misfires.

It is a Wranglerfix PCM. I might put my old one back in to compare. Andy

Timeline:

July 5th 2023 - replaced the PCM
January 17th 2024 - replaced all four O2 sensors due to P0133
January 4th 2026 - replaced 1/1 O2 sensor again due to intermittent P0133
June 2026 - intermittent violent shaking started, P0300, P0172 along with P0133

NGK - NAPA Andy

I've been doing a bit of driving with my old PCM and it is so smooth on the idle and acceleration! Much nicer. So far no shuddering and no codes. Also no hard shifting into second like before when I used it (?!).

I talked to Jay at Wranglerfix and it would be $270 for diagnostic and repair of the Wranglerfix PCM. Doesn't seem much point paying that unless my original PCM starts acting up again so I will see how it goes with the original for now and put the Wranglerfix unit on a shelf.

Looking at my records I got 5,489 miles out of my Wranglerfix PCM.

Andy