How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Steve Your Own Question
Steve, Service Manager
Category: Chevy
Satisfied Customers: 5494
Experience:  25+ Years experience as a professional working automotive technician; ASE L1 master technician
Type Your Chevy Question Here...
Steve is online now
A new question is answered every 9 seconds

I am receiving 2 errors on a 2004 Chevy Blazer - P0155 & P0141.

Customer Question

I am receiving 2 errors on a 2004 Chevy Blazer - P0155 & P0141. I have replaced the 3 O2 sensors and just installed a new Mass Airflow Sensor that cleared the error I was getting from that. Any ideas on where I should look next?
Submitted: 8 years ago.
Category: Chevy
Expert:  Steve replied 8 years ago.

These fault codes indicate that the amount of current flow through the oxygen sensor heaters is incorrect.

The P0155 is for the bank 2 sensor 1 heater circuit, and the P0141 is for the bank 1 sensor 2 heater circuit.

These heater circuits are pulsed on and off by the powertrain control module to control the heating elements inside the oxygen sensors. Performing the manufacturer's test sequence for these 2 codes requires use of a professional level scan tool that has the capability of commanding the heater circuits to pulse during testing. I am not sure if you ahve this equipment; you pulled codes somehow but I am not sure if it was with a generic code reader tool or a class-2 scan tool.

if you do not have the required equipment to perfrom the manufacturer's test procedure for this problem, basically all you can do is perform a visual inspection of the wiring harness and connectors for damage, and perhaps use an ohmmeter to check for open heater circuits or a short to ground in the heater circuits. This may or may not reveal the source of the problem, depending on whether it is an internal PCM fault, a wiring harness fault, or incorrect/ out of to,lerance heaters in the sensors themselves (not unusual if the sensors are aftermarket ones from a discount parts store, for example).

On the bank 1 sensor 2 electrical connector, the heater power circuit is supplied on the pink wire. The PCM pulses ground on the brown wire to control heater operation.

On the bank 2 sensor 1 oxygen sensor, the power is supplied on the pink wire and the PCM pulses ground on the lt green wire to control heater operation.

Power for the oxygen sensor heaters originates at the 20 amp fuse albelled "oxygen" in the power distribution center; you should have power in the pink wires whenever the key is in the ON position. If not, check for a blown fuse; if one of your original oxygen sensors had a heater shorted to ground internally it might have blown the fuse.



Customer: replied 8 years ago.
Sorry, I guess I should have included the scanner and sensor information. I have a Actron CP9175 AutoScanner, and I used Bosch 13193 sensors for the replacements. I don't believe that the scanner has the ability to test the heater circuits. The fuse looks good, so it seems I will have to start tracking down the wiring next or take it into the shop.
Expert:  Steve replied 8 years ago.

From what I see in their advertising, the Actron CP9175 is a code reader tool only; it does not seem to ahve any ability to display any live powertrain control system data or to command actuation of system components.

Have you checked for battery voltage at the pink wires at the oxygen sensor heater plugs? You may have a blown fuse...

Steve and 3 other Chevy Specialists are ready to help you
Customer: replied 8 years ago.
I will check the power and see where to go from there. Thanks for the assistance!
Expert:  Steve replied 8 years ago.
thanks for the accept; let me know if you need further assistance with this problem...