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Steve, ASE L1 Master Technician
Category: Cadillac
Satisfied Customers: 5494
Experience:  25+ Years experience as a professional working automotive technician; ASE L1 master technician
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My 2003 Cadillac Cts check engine light came on codes showes

Resolved Question:

My 2003 Cadillac Cts check engine light came on codes showes the o2 semsor need to be replaced on bank 2 sensor 2 i replaced it and had the code reset and now when the light comes on the code shows no activity i checked the fuses what could this be
Submitted: 7 years ago.
Category: Cadillac
Expert:  Steve replied 7 years ago.
   Something to remember about fault codes is that codes never indicate a specific part has failed, only what system or circuit is not behaving normally.     Do you ahppen to know the exact fault code number your car is storing in memory? There are numerous oxygen sensor related codes, all with different test procedures and possible causes...
Customer: replied 7 years ago.
The codes are P0160 and p0161
Customer: replied 7 years ago.
p0160 and p161
Expert:  Steve replied 7 years ago.
   The P0160 indicates that the rear oxygen sensor has insufficient crosscounts; that is that the signal is not varying above and below 450 mv at a normal rate.

Hhe P0161 indicates that electrical current flow 9amperage) through the oxygen sensor heater circuit is outside normal operating range.

   Have you checked for power and ground at the heater circuit pins in the O2 sensor plug yet?
Customer: replied 7 years ago.
i dont know wht those are is that where the sensor is plugged in ?
Expert:  Steve replied 7 years ago.
   Apologies for the delay in responding; I have not forgotten about you.   My online information service has been down for most of the afternoon, making it impossible to look up detailed information on your vehicle.

    Yes, you would want to go to the sensor plug and check for power and ground in the heater circuit.   I will be glad to look up which wires in the plug are the power for the heater and teh ground wire, if you wouldlike me to; however its now 530 PM and i still dont have informationa ccess yet so it may be tomorrow untill I can resume helping you with this.
    If you would like me to continue tomorrow, I willb e glad to do so; or if you prefer that I opt out of your question to open it back up to the other guys on the site to be able to jump in an assist you this evening I can do that as well...

Customer: replied 7 years ago.

I will check for it tomorrow with you

Expert:  Steve replied 7 years ago.
Thanks for being patient;
   The first rtest that is in the diagnostic sequence for this problem is to measure the resistance through the sensor heater element using a digital ohmmeter.    Unplug the sensor, and measure the resistance (on the sensor) between the pin that the yellow wire conencts to and the pin that the pink wire connects to.   We are looking for a resistance of between 2 and 20 ohms.    I realize this is a new sensor, but if it is an aftermarket sensor from a discount parts store many of them are not within manufacturer's tolerance and will cause this code to set as a result.   We need to verify correct resistance through the sensor heater element to ensure it is not contributing to the problem.

   With the engine running and teh plug disconnected, use a DVOM to measure voltage betwqeen body ground and the pink wire in the harness side of the plug.
    If you let me know what resistance and voltage measurements you come up with, it will tell us what direction to proceed in next...
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