I'm bringing this thread back from the dead to see if anyone can help me figure out why I the following codes after fitting 4 original bosch O2 sensors a couple months ago.

P0135 = Oxygen sensor heater upstream catalyst bank 1 drive cycle C - Signal too low
P0155 = Oxygen sensor heater upstream catalyst bank 2 drive cycle C - Signal too low
P1000 = Lambda Heater Upstream catalyst bank 2 Drive cycle C , signal missing

I swapped out the ECU and got same results. Reset adaptive values on both ECU's same result.

Have you checked the resistance of the heaters in your sensors Ray?
Have a look at this.
I'd suggest trying the BMW/ Bosch data first

Since it's a different topic, it might be better to create a different thread for it.

It's not like it costs anything :-)

Or just keep it in the same thread so we can keep track of it, so we aren't trying to reply in 2 or 3 places every time...

Be careful not to measure/put multimeter across the actual sensor pins on the bosch sensors.. I'm sure I killed my old pair doing that, since they generate the voltage themselves.

I'd also check heater resistance, and maybe even voltage getting to heaters when it's switched on.

What live data does nanocom show for them, do they ever heat up enough to start switching?

gordonjcp wrote:

Since it's a different topic, it might be better to create a different thread for it.

It's not like it costs anything :-)

True but all the info is here related to the previous testing I did.

Martyuk wrote:

Or just keep it in the same thread so we can keep track of it, so we aren't trying to reply in 2 or 3 places every time...

Be careful not to measure/put multimeter across the actual sensor pins on the bosch sensors.. I'm sure I killed my old pair doing that, since they generate the voltage themselves.

I'd also check heater resistance, and maybe even voltage getting to heaters when it's switched on.

What live data does nanocom show for them, do they ever heat up enough to start switching?

I looked on the Nanocom and one of the 2 is switching. The other one sits at 0.44
All this testing sounds like fun in a shitty Canadian winter without a garage. I will have to pull the ecu and test the heater circuits and if there is an issue I will have to crawl under and test again at the sensor connectors.

Orangebean wrote:

Have you checked the resistance of the heaters in your sensors Ray?
Have a look at this.
I'd suggest trying the BMW/ Bosch data first

I will take a look at this in the next day or so and do some testing.

I have tested all the wiring. I have same results as before. All good between fuse 26 and O2's. All good between ECU and O2's.

Both sensors are getting 12v when ignition is at position II.

Both sensor heater circuits are showing resistance of 2.0 which good according to the link Orangebean posted.

Maybe a ground issue?

It's got to be worth investigating the ground issue, or something along those lines.

Did you check the heater resistance just across the sensor? I wonder if it's worth checking it at the ECU - in case the wiring is a bit worn and upping the resistance?

From memory the sensors are grounded by the ECU - and just looking at RAVE, they all end up in the same connector - C0635 at the engine ECU (sensor wires, plus heater grounds) so that might also be worth a look at too...

I seem to remember awhile ago with your O2's being a problem that you were sent the wrong ones by a seller? Did they end up sending the correct sensors in the end? And were they genuine ones when they arrived?

I cleaned the connector at the ECU and put it all back together. I have since not got the 3 codes above but had one for the rear O2 sensor catalyst deteriorating. There is no cats and I have pulled the O2's from the stream with spacers. I also put a new set of spark plugs in which made a huge difference. I am just going to leave it alone for now. -20C sucks!
Resistance readings were all identical on all the wiring from the O2 connector to ECU connector. No issues.
The O2's are genuine bosch bought from Rockauto.

OK I got this sorted. I had stressed the terminals in the connector C0635 at the ECU when I was probing them. After I took all the effected terminals out and tightened them up all was good. No more check engine light at all.

Good to hear!