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Dan
Dan, Technician
Category: Buick
Satisfied Customers: 24574
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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I have a P0135 error and I have done everything I can do to

Customer Question

I have a P0135 error and I have done everything I can do to fix it but still can't get it to go away. The only thing I can think of is the engine is causing the error but can't think of what it is
I have replaced the ecm the O2 sensors 3 times for each one and replaced the exhaust system and the catalytic converter and changed all the relays and repaired all ground wires and checked the wires from the ecm to the O2 sensorand they are working fine with the right voltage and the O2 sensor is closed like it should be. Please help!
Submitted: 2 years ago.
Category: Buick
Expert:  Dan replied 2 years ago.

This code is for the bank 1 sensor 1 oxygen sensor heater circuit which would be sensor closest to engine on front exhaust manifold.

Expert:  Dan replied 2 years ago.

Have you checked the pink wire for power on cold start at sensor?

Expert:  Dan replied 2 years ago.

The black/white sensor should also get ground at first start up. Depending on which one your missing would determine the next step. Let me know, thanks.

Customer: replied 2 years ago.
I did
Expert:  Dan replied 2 years ago.
Did it have both power on pink wire and ground on black/white wire during problem?
Expert:  Dan replied 2 years ago.

During cold start is when you would want to check.

Customer: replied 2 years ago.
I did that and it had p I wrong a cold start
Customer: replied 2 years ago.
Sorry yes it had power on the cold start
Expert:  Dan replied 2 years ago.
Thanks, ***** ***** also check for ground on black/white wire?
Customer: replied 2 years ago.
Expert:  Dan replied 2 years ago.

Did you replace sensor with OEM AC delco sensor?

Customer: replied 2 years ago.
I did that as well
Customer: replied 2 years ago.
I am at a complete loss the only thing I can think of that is causing the problem is something the engine is doing to cause the check engine light to come on and to give me the P0135 error code
Expert:  Dan replied 2 years ago.

I'd consider double checking power on pink wire and ground on black/white wire because I think one of the two must be missing. You can also use a headlight to test the power/ground so you know the wiring/connections can handle the load. Let me know how test goes or if you have more questions. I know you do not want to test it again but I think it is required at this point. Let me know if you have more questions, thanks.

Expert:  Dan replied 2 years ago.
Make sure to check oxygen sensor connector condition, it is possible a loose pin is causing this.
Customer: replied 2 years ago.
I already did that and I even tested it to see if the voltage is correct and it was on all the wires
Customer: replied 2 years ago.
Checked that as well
Expert:  Dan replied 2 years ago.
What was voltage reading on pink wire?
Customer: replied 2 years ago.
12.4 volts
Expert:  Dan replied 2 years ago.

Did it maintain 12.4 volts under load?

Customer: replied 2 years ago.
Yup
Customer: replied 2 years ago.
The O2 sensor is supposed to be closed correct
Expert:  Dan replied 2 years ago.
vehicle starts in open loop when cold and oxygen sensor heater helps it warm up so it can go into closed loop quicker.
Expert:  Dan replied 2 years ago.

Do you have scan tool capable of monitoring oxygen sensor heater current flow?

Customer: replied 2 years ago.
Could it be something in the engine like a mass flow problem or something
Expert:  Dan replied 2 years ago.

No. This code can ONLY be sensor, wiring/connector, or ECM. That is why I say I'd double or even triple check power/ground at sensor again. If your 100% sure that the pink has good voltage and other wire has good ground then replace the oxygen sensor again. Let me know how it goes or if you have more questions. Thanks.

Expert:  Dan replied 2 years ago.

P0135 Heated Oxygen Sensor (Bank 1 Sensor 1) Heater Circuit Malfunction - With Automatic Transmission

Possible CausesSetting Conditions

  • HO2S connector is damaged (check pins for damage, and for moisture)
  • HO2S heater low control circuit is open, or shorted to ground
  • HO2S heater reference circuit is open, or it has a high resistance condition
  • HO2S heater ignition circuit is open (check OXY SEN fuse in U/H fuse block)
  • HO2S heater has failed
  • ECM has failed

DTC P0030, P0053, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496 and P2135 not set; and DTC P2A01, P0401 and P0420 not commanding fuel; engine runtime over 100 seconds, engine speed from 600-3,000 rpm, system voltage from 9-18v, ECT signal more than 149ºF, MAF signal from 4-30 g/sec, HO2S-11 Heater not commanded "on" with the Scan Tool, conditions met for 2 seconds, and the ECM detected the HO2S-11 heater current was less than 0.24 amps or more than 0.94 amps for at least 17 out of 20 samples. This diagnostic can run up to 5 tests per trip, with a delay period of at least 30 seconds between tests. The test duration is one second.

Customer: replied 2 years ago.
Do you mean a curent reader like the black and red wires that connect to a control box that gives you the voltage readings
Expert:  Dan replied 2 years ago.

Here is information from manual for code too https://www.dropbox.com/s/8xnx39qtilipjta/p0135.pdf?dl=0 Let me know if you have more questions. Thanks.

Customer: replied 2 years ago.
Where can I get that sc a nner
Customer: replied 2 years ago.
Sorry where can I get one of those scanners
Expert:  Dan replied 2 years ago.

No, there is a specific option in scan tool to check current. The multimeter you are referring to would work also. At this point I'd triple check power/grounds to oxygen sensor. If you connect pink wire to one bulb terminal and black/white wire to other terminal. If bulb turns on bright on cold start then replace the oxygen sensor again. If not, then you have a wiring problem. The scanners are really expensive so not worth buying if you don't already have one. Let me know if you have more questions, thanks.

Customer: replied 2 years ago.
Thank you for your help I just don't know what it could be actually. I have spent so much money on this car especially on this one issue. I guess I can check it again but I seriously doubt that is the issue but thank you for your help. I would like to get my money back but you have been very helpful so I won't Thank you and have a great night
Expert:  Dan replied 2 years ago.

I know how it feels when chasing problems....after awhile it feels like it must be something crazy but I think if we go over the basics again we can find the problem. Let me know how test goes with bulb in the morning, you can reply back to this answer at any time without additional fees. Thanks again and have a good night.