65ChevyIINova

I started to get P0154 and P0134. No activity detected in oxygen sensor for bank 1 sensor 1 and bank 2 sensor 1.

I have an LSX conversion where the heaters for both o2 sensors are on the same circuit. If the heaters were not working would this code pop up? I am not able to check this with my diagnostic tool.

The diagnostic tool says the o2 sensors are sending around 440 mV but the system will not go into closed loop because it is saying neither sensor is responding?

Since I can see a signal in the computer/diagnostic-tool then I though maybe the heaters are bad and it is throwing a code since it is taking too long for the sensors to warm up.

Both sensors are new and the engine/sensors only have about an hour of run time on them.

Any thoughts?

Cheers
Bret

jimmyblue

iTrader: (11)

When some sensor codes pop, the PCM will jam the one(s)
it's pissed about to about 490mV (may vary) and there
they will sit. Will your tool clear codes? Try that and see
if the sensors start responding (for a while, until the PCM
gets annoyed again).

2xLS1

iTrader: (25)

Have you checked for 12V and ground on the heaters?

65ChevyIINova

I just checked the circuit that supplies power to the heaters and it is at least sending 12 volts. I need to crawl under the car to see if the wires underneath are still getting 12 volts.

I have tried to reset the code a couple of times but it will come back within a few minutes. When I reset it, I did not check the voltage to see what the signal was doing. I will try that today.

Old Geezer

iTrader: (3)

During that 1 hr run time, did they ever work?

65ChevyIINova

I honestly don't know, I never dug that deep into the reader to check their response until the check engine light came on. It is possible that they have never worked, but I would think the code would have come up sooner?

Is there a way to test the 02 sensor to see if it is actually working? At $50 a piece I would like to check before spending a bunch of money.

If an o2 sensor gets clogged with oil will it be obvious to see this with a visual inspection?

Thanks again for the input guys.
Bret

65ChevyIINova

I checked the bank 2 o2 sensor and it seams to be fine, both the heater and signal.

I am going to check the signal wires leading from the PCM to the sensor plug. I will give an update tomorrow when I know all my wires are right.

jimmyblue

iTrader: (11)

You can test sensors with a propane torch and a DMM
(a neutral flame fully covering the element ought to
give you 0.5V). But this is only a gross functional kind
of check, leaving out the issues of thermal conditions,
slowness etc.

2xLS1

iTrader: (25)

All you have to do is with KOEO, as the heaters heat up, look for the O2 sensor voltage outputs to start lowering from 450mv to 200mv or less with the sensors still installed in the pipes.

jimmyblue

iTrader: (11)

Does this work if the PCM has pre-faulted them and is
holding the voltage to center?

2xLS1

iTrader: (25)

I don't know that the PCM does that like you say it does. I've seen plenty of O2s still switch with O2 codes set. I've always believed it the 450 mv is just a bias voltage through a resistor that the O2 pulls up or down. I should have added that you need to perform the KOEO test on a cold O2. The Diadnostic procedure says that if the O2 stays between 300 and 700 mv, the heater is bad,

65ChevyIINova

So both o2 sensors seem to be good. They show voltage when you do the torch test and both heaters have good resistance (so I don't think they are bad).

I checked all the wires and I get 12 volts on the heater lines. I checked the signal high and signal low; both are still connected to the PCM. I checked this by checking resistance of the signal wires. Then I checked to make sure all the pins are plugged into the correct spots on the PCM.

So now I am stumped...

Anything else that could cause this to be happening? Could something be wrong with my PCM? Does the computer have to see other inputs from other sensors in order to complete the o2 sensor checks?

Cheers
Bret

2xLS1

iTrader: (25)

You need a scanner with bi directional controls that you can force closed loop on with. I've seen O2s not switch until closed loop is forced. A little more information on the vehicle/pcm/os/wiring harness would be useful.

65ChevyIINova

I might have found a problem, but too late to mess with it tonight.

I was just reading that both o2 sensors low-references are supposed to be tied together and also tied to the blue 63 pin on the PCM. I don't remember doing this when I wired it. I just checked my PCM and I have a yellow wire going to this pin and not a tan like what is listed as the low reference. When I wired the PCM I am pretty sure I used all the original wires so this should be tan...

Looking at 2 different web sources for a 2001 vortec, blue pin 63 is either a temperature sensor ground or a ground for o2 sensors... Can anyone else chime in on this?

Could a poor low reference cause this? I am going to verify/fix this tomorrow and see what happens.

http://lt1swap.com/pictures/isolated..._schematic.gif
http://lt1swap.com/99-02_vortec_pcm.htm

65ChevyIINova

OK, so since I have isolated ground o2 sensors. Blue Pin 63 is supposed to be tied to the grounds for my sensors that are Blue-26+29

For isolated ground o2 sensors the ECT is supposed to ground to blue 41.

Will check this tomorrow after work.

65ChevyIINova

The car is a LSX converstion. The engine is originally out of a 2001 Chevy 1500. The transmission is now a 5 speed manual and not the stock 4l60E. The PCM is the stock PCM that was re-tuned to update for the stand alone setup. I am only running 2 o2 sensors B1S1 and B2S1. Both sensor 2's were supposed to be turned off. The only sensor I changed in the system was the MAF to the Card style GM MAF.

When I wired the conversion I did not run the vss to the PCM. It goes straight to my gauges. I also did not run my brake switch to the PCM. I was told this was only needed for the 4l60E and not a manual transmission.

So I went back and tied all my low references together like the original GM diagrams (Blue pins 63, 26, 29), reset the codes and no change. I get 12 volts on my heaters. These are wired to turn on with the key and grounded to the frame. This does turn on with the key. My 02 signal wires are wired to blue pins 66 and 69.

This is how I have my o2 sensors wired, minus B1S2 and B2S2 were removed. I also removed the low reference pins for the second o2 sensors. This is also how I got my harness from the original truck. Note the heaters do not go to the PCM in my setup but in the other schematic they do.



I did not wire my o2 heaters to the PCM like this since I found info saying this was only done on 6 L engines.




If my wiring is good I will have to go to a shop to use a tool that will force a closed loop. My scan tool will not do a whole lot. If I hook it up to my stock truck I can run a KOEO test but when I hook it up to the problem car it will not allow me to run a KOEO test.

Cheers
Bret

2xLS1

iTrader: (25)

The B1S1 and B2S1 signal pins are C69 and C66. The low reference pins are C26 and C29. You say you are tying 63,66, and 69 together. That is not right unless you typed your reply wrong and got your numbers mixed up..

65ChevyIINova

That was a typo (fixed in original post). i verified on my pcm. purple signal wires go to 66/69