giffordj

So driving home a few days ago, I get the check engine light with a code P0443. Mechanic is leaning heavily towards ECM, but based on some reading I'm ruling it out. The following is the list of events that occured

P0155 - 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
P0161 - 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)
P0443 - Evaporative Emission Control System Purge Control Valve Circuit
Check Engine Light Comes on at this point
P0135 - 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P0155 - 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
P0141 - 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P0161 - 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

Any Ideas where to look, or does it appear to be a bad ECM?

This is a Mustang GT 2005

imp

Yer in luck! I got P0155, no other, replaced all 4 sensors, no change, P0155. Checked sensor heater resistances, all within spec; good, high resistance to ground. Then, started getting p0156 also (heater resistance, 2-2.). Disconnected wires feeding heaters, put in all new wires, same g#d-damned thing.

Then I read somewhere the heater resistance codes are used to indicate certain cat malfunctions. My rig has 165k+, original cats, so definitely possible. That's where I'll go next. The heaters work fine, electrically everything checks. BTW, I replaced the ECM, no change!

If you have lots of miles, or even if not, look to the cats! imp

giffordj

Update, Mechanic didn't do anything and code has seemed to go away. Previously my mechanic replaced the Control Valve Solenoid, but refunded me since it didn't fix the issue. He checked for a short, didn't find anything. Checked fuse 47, no issues there. Any ideas?

Derf00

I would ignore P0443 for now and focus on the O2 sensors. The harnesses for the rear O2 sensors are down UNDER and behind the bell housing of the transmission, most likely under a black plastic cover.. Check those connectors and wires first for shorts, burnt or exposed wires. Also check your Front O2 sensors for the same.

Have you had any type of work done on the car before it started having problems or did you drive through any deep water?

giffordj

No work done on the car. No deep water. Now I took it to the Ford Dealer they didn't find anything wrong as well, they just reset the ECU and everything has been fine since. But I did notice they did do something in the front fuse box, the fuse in 47 was newer. (I put a dot with a sharpie on it)

Derf00

Faulty fuse? Unusual for ATC blade type fuses but not entirely unheard of.

giffordj

Update the light came on again. My mechanic after replacing everything still the code keeps coming back, he's thinking it's a short somewhere in the system. Have an appointment Wed with Ford to look at this.

giffordj

Update from the Dealer, I have a short in my PCM. Looking for a PCM now. The Dealer wanted 2k, kinda of crazy since they are all re-manufactured.

giffordj

Was able to get the PCM repaired, everything is working great. Repair was $200.

imp

Good news! It is fairly unusual for PCMs to go bad, and when they do, it takes either a hit/miss replace or testing by specialized dealer equipment. imp