Focus SVT - O2 vs ECU

So my 2003 SVT Focus threw a P0135 O2 Heater code a few months ago and I just recently got my mechanic to throw in a new front O2 sensor. Same code is still throwing so I did some research and it turns out the O2 sensors (at least the heating for the O2) are on their own circuit on fuse #18. As the interwebs indicated fuse 18 was blown. I replaced the fuse and the CEL came back on pretty quickly, so I suspect fuse 18 is blown again.

So with further web surfing it looks like one of 3 things. a) it is actually the rear O2, no big deal or b) a short, I have neither time or skills to locate so back to the mechanic or c) the ecu needs to be replaced.

If I get lucky my mechanic may find a fix with either a) or b) but I don't want to pay these guys for days on end of troubleshooting. If it points towards the ECU, any thoughts on how to be sure it is the ECU?

If I need to replace the ECU I have to deal with a used part and the Ford PATS security (suckage = Ford dealer.) So the follow up question is:

If I find a used SVT ECU with a set of matching keys, would I be able to temporarily tape the new keys with the PATS transponder matching the new ECU to my steering column in order to use my current keys to drive the car to the Ford dealer to get the ECU/PATS reprogrammed?

Did you replace the sensor with an OEM Part? The SVT's seem to be really picky about O2 sensors.

Mitchell wrote: Did you replace the sensor with an OEM Part? The SVT's seem to be really picky about O2 sensors.

This.

Yes, make sure you use OEM sensors.

P0135 - HO2S Sensor Circuit Malfunction (HO2S-11) During testing the HO2S Heaters are checked for opens/shorts and excessive current draw. The test fails when current draw exceeds a calibrated limit and/or an open or short is detected. Short to VPWR in harness or HO2S. Water in harness connector. Open VPWR circuit. Open GND circuit. Low battery voltage. Corrosion or poor mating terminals and wiring Damaged HO2S heater. Damaged PCM. Wiring. Damaged HO2S heater. Damaged PCM.

With the blown fuse it sounds like a short in the wiring to me. This usually occurs in the second O2 sensor since it is in a position that can be hit by road debris, etc.

P0135 is bank one. that means the one in the exhaust manifold or close. As Hal said, sounds like a short to ground.

I did order the front O2 from a Ford Dealer and I will do the same for the rear O2. I am hoping the rear sensor is the key.

iceracer wrote: P0135 is bank one sensor 1. that means the one in the exhaust manifold or close. As Hal said, sounds like a short to ground.

FYP. (there's only one bank on a 4 cyl engine anyway).

The code as written in my OBDII book that we get every few years-

"*** P0135 O2 Heater (HTR-11) Circuit (bank 1, sensor 1)"

The *** means it lights the MIL light.

All the heaters ground through the harness, not the manifold. That's why there are two white wires. What sucks about that particular code- it does not tell you if it's an open or short- which isn't really a hard test to perform.

For sure, though, it's not the catalyst monitor (or second) sensor, it's the front one, just like iceracer points out.