OK I have now done some meassurements, it seems that there is a cable problem to the CPU.

I have done these steps from the diagnostic document.

Step 5. Turn ignition off. Disconnect affected HO2S connector. Turn ignition on, with engine off. Connect a jumper wire between a known-good ground and HO2S harness connector terminal "B" (Purple/White or Purple wire). See Fig. 6 or Fig. 7 . Connect a jumper between a known-good ground and HO2S harness connector terminal "A" (Tan/White or Tan wire). Observe HO2S voltage on scan tool. If HO2S voltage is less than 200 millivolts, go to step 9. If HO2S voltage is not less than 200 millivolts, go to next step.
Voltage was less then 200mV

Step 9. Remove jumpers wire. Check OXYGEN fuse located in underhood fuse block. If fuse is open, go to step 12. If fuse is okay, go to next step.
Fuse is OK

Step 10. Turn ignition on, with engine off. Using a test light connected to ground, probe HO2S harness connector terminal "D" (Pink wire). If test light illuminates, go to next step. If test light does not illuminate, go to step 17.
Light illuminates, I have 11.6V

Step 11. Connect test light between HO2S harness connector terminals "(" (Black wire) and "D" (Pink wire). If test light illuminates, go to step 15. If test light does not illuminate, go to step 18.
Light illuminates. I got 0.38V between A & B. Between C & D I have 11.6V

Step 15. Turn ignition off. Check for poor connections at affected HO2S harness connector. Repair as necessary. After repairs, go to step 21. If connections are okay, go to step 19.
Sensor and connector are new, probably cable problem further up the harness.

So my next step would be to connect new cables from the CPU down to the connector. But where in the connectors are these two cables connected?

Thanks

 

I’ll look at this tonight

George

 

The 4 wires on your O2 B1S2 are:

Brown heater low to pin 72 PCM C1
Pink heater high Oxygen fuse in UHFB
Tan sensor signal lo goes through S100 then on to pins 28 and 29 PCM C1
Ppl/wht sensor signal hi pin 68 PCM C1

That gnd splice for the sensor lo is a possibility if its that wire. Here are the pages out of the 2002 manual for the test procedure as well as the PCM connector layout:








George

 

Thanks George for all the info.

I went through the diagnostic procedure and came to step 9 where it says that I should check the low reference circuit between Connector terminal A and PCM C1-63 for connection. I ended up there since there is no cable going to C1-63. I saw the cables you mention in C1-28 and 29 being the Tan as going to the connector. Didn't give any closed circuit there when I checked with my instrument.

So we probably have a bad cable going there. But since there are two cables coming there where or on which one should I go from with a new cable down to the connector.
Where is S100 you mention?

Thanks, much appreciated!

 

There must be different Pinouts by year and that’s why I including all those charts and diagrams. I just so happen to also have a 2002 so my shop manuals apply to you as well. I will look tonight to see if the manual gives a location for that lo ref splice (s100), I do not know off hand. I don’t think it makes any different which of the two lo ref pins you connect to (28, 29 or both).


George

 

Yes since they join that S100 I should connect to both pins since I will go with a new cable all the way from the PCM down to the connector.

I'll do it tomorrow, started to rain now, and report back.


Thanks

 

George, I found the correct pinout diagram



It was Pin 28 that go to the B1S2 connector and that cable is OK, I get signal from my test tool, Same with the high connection at Pin 68.
I also checked the power and ground to the connector and they are OK.

I can't find anything wrong with that cables to this sensor.
But if I follow the diagnostic it results in some cable problem.

I'm lost here.

On top of that when I now have put everything together I have problem with the idle when selecting gear. It goes down to 300 rpm and engine dies. I guess that is another subject.

Thanks

Jan

 

The reason why I sent the manual pages is because your original test procedure had some wrong wire colors and I don't know what those connect pins are (A. B etc). Lets go at this another way and describe how this works:

At key on for a cold engine The heater element needs to turn on to get the O2 sensor up to operating temperature for it to work properly. This requires:

1) 12v on the pink wire from the oxygen fuse and a trouble free wire connection so that voltage is maintained at heater current
2) The proper switching of the brown wire to ground by the PCM to complete the heater circuit and a wire that has no issues at full current

Then the sensor circuit has to work properly:

1) A bias voltage of 0.45v needs to be presented to the sensor on the ppl/wht wire and the wire run needs to be clean
2) A good lo ref signal ground on a clean wire needs to be presented to the other side of the sensor on the tan wire.

The sensor itself needs to function properly and take the 0.45v ref voltage and present a slowly drifting voltage back to the PCM of between 0.45 and 0.7V after it and the cat heats up. The output should follow the upstream sensors on a cold engine at start up

The PCM has to do everything above correctly.

The procedure is trying to determine if you have the following:

1) Solid 12v on pink
2) Proper ground switching on brown
3) 0.45v ref on ppl/wht
4) Clean signal ground on tan.
5) working sensor
6) working pcm

With sensor diconnected:

An incandescent test light across pink and brown proves the heater circuit

A voltage test of ppl/wht to tan proves the 0.45v ref voltage. Continuity of those two wires between the pcm and connector indicates a good circuit unless there is a marginal wire fault that only reveals itself at temp or under sensor load. A marginal wire could inject some tail chasing at this point. Some like to watch the ref voltage on a scanner with the sensor disconnected and then watch it go to zero when grounding the signal wire. If all that tests OK then switch sensors and see what you get.

What is the sensor value in live data? What do your fuel trims look like?

George

 

OK, I'll do another check.

I was thinking that I might have connected it in a wrong way.

First I bought a new sensor, this one:
More Information for BOSCH 15896 (rockauto.com)
And I still got the P0140 error, I then bought a new connector and connected it to what I thought was the correct way, I looked at the old connector and used it's pin in the same way.
But maybe the new sensor is connected in another way. Is that likely??

Today when driving after I had done the cable checks I got a P0101 error together with the P0140. I saw somewhere that the MAF can trigger a P0140, but I have never seen the P0101 before on this car.
BTW the idle problem I mentioned is gone, it must have been some glitch.