: 2001 Catera throttle body and O2 sensors

01-28-13, 11:41 PM
Hi Folks,

If the throttle body is bad could it cause O2 sensors (bank1 sensor 2 and bank sensor 2) to act up and throw a CEL. I replaced the O2 sensor on one side but still getting code no heater circuit and other side I don't remember the description exactly but both were the O2 codes.

I ran a live data with my code reader and it was reading the O2s so not sure why it would say no heater circuit.

Any help is appreciated.....thanks.

01-28-13, 11:48 PM
How about swap the O2 sensors, or the connectors if you can, and see if the code changes.

01-29-13, 12:23 AM
okay, I'll try swapping the O2s not sure if that'll make any differences because my scanner with live data was reading it.

01-29-13, 06:13 PM
I only suggest that as a starting point just to rule out the oxygen sensors. If the codes don't change, then you can rule out the O2 sensors. You can also check that you have 12vdc on at least one of the wires on the connectors. If you don't you might have a blown heater ckt fuse. The heater ckt is separate from the sensor ckt which would explain that you are still getting a reading from the sensor.

01-29-13, 08:29 PM
Okay, thanks. How do I check for the 12vdc and where's this fuse located? Also, when the code P0161 (bank 2 sensor 2) came on at first I replaced the sensor with a new one from rockauto.com (APWI Part # AP4251) and then the next day CEL came on and it read two codes P0161 (bank 2 sensor 2) and P0140 (bank 1 sensor 2 heater circuit).

My question now is, could the new sensor (APWI part #AP4251) have cause this problem?


01-30-13, 12:13 AM
First off, I see your getting codes 160 and 161?? My service manual shows both of those codes for bank 2 sensor 2. Did you replace the correct O2 sensor?

DTC P0160 HO2S Circuit Insufficient Activity Bank 2 Sensor 2
DTC P0161 HO2S Heater Performance Bank 2 Sensor 2

01-30-13, 12:27 AM
sorry one of the code is P0140 instead of P0160

yes, replaced the O2 post cat (passenger side) bank 2 sensor 2 code P0160 came on first. The next day code P0140 came on so not sure what to do. I couldn't locate the fuse for the O2 either.


01-30-13, 04:39 PM
Make sure the key is off, then disconnect the O2 sensor at the connector. Turn the key on. With the black lead of the mulitmeter, find a good ground point on the chassis. Connect the red led to one of the pins on the connector that goes toward the engine. Check the pins until you find one with 12vdc. This is the heater voltage from fuse 43 in the ECM. Check the connector of the sensor on the opposite side as well. (don't worry about the fuse just yet)

01-30-13, 06:34 PM
Okay, thanks. I checked the voltage and getting 12vdc at both sides of the O2s so pretty sure the fuse is good. Also, the CEL came back on this morning after I turned it off last night. I scanned it this afternoon and it showed only P0140, bank 1 Sensor 2 heater circuit. Any idea where to go from here for this code?

Anyways, I swapped the sensors, cleaned the connectors and secured everything back. I'll let you know if CEL comes back on again.

01-31-13, 11:06 PM
Okay, here is the update...

After swapping the sides on the rear O2 sensors we drove around and there was no CEL. Then this morning the CEL came back and it read the same two codes P0140 - O2 Circuit No Activity Detected Bank 1 Sensor 2 and P0161 - O2 Heater Circuit Bank 2 Sensor 2. I checked voltage last night and it was reading 12Vdc at both connection.

Also, when I checked the resistance on the old O2 sensors it was showing 8.5 each whereas the new one from rockauto.com APWI part #AP4251 was showing a resistance of around 13.

I have no clue what to do now, either get another sensor for the other side and see if it'll fix the O2 issues or track some other problem in the system.

Also, should I stick with Bosch brand O2s or the APWI will be fine? I checked with rockauto and they said they have been selling APWI O2 brand for the past year and had no problems.


02-01-13, 05:17 AM
May be a "stupid" question, but are you clearing the codes after replacing the O2 sensors?

IIRC, once a code is set, it stays in memory until cleared. (That used to be the case, I haven't thrown a code in several years!)

It's worth a try.

02-01-13, 10:31 AM
Yes, I have a code reader / scanner where it can read live data and clear the codes.

I just not sure what to do now.

02-02-13, 09:01 AM
Any other tips what I should do to figure out these rear O2 CELs, should I buy another sensor?


02-02-13, 09:39 AM
these cars are definitely not happy with many aftermarket O2 sensor brands ... bosch sounds like it might have been the OEM supplier but i can't remember

stick with the ACDelco part if you can

02-02-13, 11:34 AM
Just to clarify, on the sensor with the 161, with the old sensor, new sensor and the sensor from the other side on the connector, you are always getting code 161? What percent or voltage does your scanner read for the sensors. Is the new sensor a direct fit or universal?

02-02-13, 04:10 PM
The new sensor is a direct fit and per rockauto.com, these are compatible and also fits perfectly. This is new brand and have sold a few of these sensors in the past year and had no problems. The voltage shows 12vdc at the connector end when I turn on the battery. I believe it's the resistance that shows 8.5 on the the old ones and the new one I got shows about 13.

The P0161 was there before changing the sensor, so got the new sensor and now I get codes P0161 and P0140 after the replacement. i swappd the sides and still get the same codes.


I'm going to try one more thing, going to install the old sensor back, clear the codes and test drive it. If the CEL comes on I'll scan it and see what it shows. If it's just P0161 then I'll return APWI brand sensor and go with Bosch or AC Delco brand sensor.

02-03-13, 02:27 AM
So, with 3 different sensors in bank 2 sensor 2, one of them being new, you always get code 161. I would say there is probably something else wrong. From the connector toward the ECM, or an exhaust leak upstream or the air distribution system. (from the service manual)
There are more tests you can do. There is a detailed troublshooting guide in the manual for all the codes.

For code 161 I'm summarizing from the manual.
Key off for at least 20 min. meter on ohms, red led to pin 3, black led to chassis ground. should be less than 5 ohms.
Key on, meter on VDC, red led to pin 1, black led to pin 2, should be 0 vdc
Start engine, meter on VDC, red led to pin 1, black led to pin 2, should be 12vdc or switching between 0 and 12v.
Engine off, jumper a wire from pin 4 to chassis ground. Key on, Engine off, scantool should read 0 volts (or 0% I would imagine) for the affected sensor.

Also, on the sensors, read the ohms between pins 1&2(the heater) then 3&4(the sensor), and compare them between the sensors.


Fused Battery Feed

HO2S Heater Control

HO2S Reference Ground

HO2S Signal[COLOR="Silver"]

02-03-13, 08:43 AM
Okay, will try it out. I don't think there's any exhaust leak bit will check again. How many ohms should it read between 1 & 2, 3 & 4?


02-03-13, 10:16 AM
Don't know, but I'm heading to the junkyard now to get a sensor for mine, sensor #1. I have a code 135. When I put it in later I can check my sensor #2 and let you know.

02-03-13, 08:28 PM
Okay, thanks. I swapped the new sensor out and installed the old one back. Now both are the old sensors on the car. I check the resistance again on the old sensors and it was 8.3 to 8.5, the new one was 13.3.

I scanned it with live data check and it was reading same numbers at both sensors so pretty sure both sensors are okay. Also, checked the connectors and getting 12vdc.

Well see what happens now.


02-04-13, 04:41 PM
did you say that you already replaced the ECM?

bad ECMs have been known to produce false positive O2 sensor codes

02-04-13, 06:19 PM
I didn't replace the ECM yet. The car's idle is also not that 100%, still thinking the throttle body might be bad.

I guess we are back to the ECM, probably causing this O2 codes and the idle issue.

02-04-13, 08:55 PM
Okay, here's the latest after installing the old sensor to the driver's side cat. The CEL came on so scanned and it shows P0140 and P0141, no more P0161 so now I think it's the O2 sensor and maybe P0161 was showing because of the new aftermarket O2 Sensor.

02-04-13, 09:09 PM
That sounds very likely. It's really hard to get these kinds of problems fixed. Even when you have experience and the factory service manual and tools available to you it can be tough.

My guess would be PCM or throttle body electronics are at fault here.

Good luck and keep us posted.

02-04-13, 10:01 PM
I think so too and going to get a Bosch sensor and see what it does. If no change then swap the ECM or Throttle Body.


02-04-13, 11:34 PM
Should I get Bosch or AC Delco O2 sensor?

02-05-13, 01:23 AM
I'd get AC Delco, but both are good.

02-05-13, 08:54 AM
Ordered the AC Delco from Amazon. It was cheaper than the Bosch.

02-07-13, 07:58 PM
The new AC Delco sensor is here and checked the resistance at the two white wires before installing it and I'm getting the same numbers like the old one (8.5). I couldn't get any reading from the gray and black wire on the sensor, similar to the old one.

Well, going to install it in a few minutes and see what it does. if I have anything new I'll be back with the update.


02-08-13, 09:36 PM
Here's the latest, installed the sensor last night and drove it around all day today and the CEL came on. I scanned it this evening and it's only showing P0140. The P0141 is no longer showing and car is still idling a little rough.

Any idea what to do next? My only guess is ECM and throttle body now.

02-13-13, 02:10 PM
Okay, so took the car to dealership and they did their diagnostic on the P0140 / O2 sensor and they said the new sensor is bad and they couldn't find any other problem. They are checking on the idle/ throttle issue now. I guess have to send in the new O2 sensor for a replacement.

02-13-13, 05:37 PM
Here's the update on my in laws car!

The dealership checked the idle / throttle response and recommended to get it cleaned and probably do a fuel injector clean. I have already done these so my guess is it's a bad throttle body. Regarding the O2 sensor now they are saying it's the old O2 is bad, so confused with them.

I'm going to check the sensor and make sure which to replace,

02-13-13, 11:32 PM
Sounds Ike they're not really sure

02-13-13, 11:52 PM
Yep, they are not sure or not interested in finding the exact problem. We paid $95 for the diagnostic and ended up no where. This afternoon they did some testing, swapped the O2 sensor side and said that the new one was bad because it gave the codes P0160 and P0161 for bank 2 sensor 2. When my father in law went to pick the car up they said that the old sensor was bad.

Who knows what's going on.....anyways I removed the new sensor and installed the old one back and will test it out.

02-16-13, 12:28 AM
Got the new AC Delco / bosch throttle body and replaced it, car is much smoother and idling better.....P0160 is still showing up on the scanner after installing the old O2 back.

I'm sending the new / possible defective O2 back for a replacement.

Also, is the new throttle body made in China now instead of Germany?


02-16-13, 08:47 AM
country of origin should be on the box
that's the only way i can tell
and i don't have one here


the code may take a couple ignition cycles to clear out (usually 3)

if it doesn't go away soon then be worried
but it sounds like there's some good progress

02-16-13, 12:03 PM
It's kind of weird the box says AC Delco 9128412 / GM 9128412 and made in China. Also, on the throttle body it has a sticker saying Bosch part number and made in China and is not like the original machine pressed imprint on the throttle body.

Anyways, the car is running better has a slight shake at cold start and not sure what that could be but runs fine after warming up. Anyways, need to replace the O2 sensor now and hopefully fix the O2 problem.


02-16-13, 12:20 PM
well that pretty much settles it

bosch wouldn't be the first manufacturer/supplier to switch to chinese production

02-16-13, 12:29 PM
I did the relearn process for the throttle and maybe after few runs it might fix that initial / cold engine shake.

02-28-13, 12:08 AM
Well after getting the second new AC Delco O2 sensor and swapping it out, the code still comes back P0160.

I think it might be a circuit problem now.