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Discussion Starter · #1 ·
Okay, I have a 2001 Ford Focus. Engine light was on. It threw codes P0135 and P0141. Easy enough, so I replaced the O2 sensors. Light went off in park. Drove around the block, back on. Same codes. Checked fuse 18, and it seemed okay. So, someone suggested I replace the plug wires. Did that. No change. So, I'm open to suggestions. If it is wiring, are there any instructions on how to check that? If it's PCM, could I just replace the chip in it? What's the cheapest options here. Ford says 800 dollars. Please help! I can't get a tag until this thing passes emissions.
 

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DTC P0606
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Look for obvious opens, shorts, corrosion in the wiring harness. It's simply a case of tracing the wiring back from the sensor end and inspecting it carefully. Usually excessive heat is the culprit or water/condensation has corroded the electrical metal prongs in the plastic connector.

What brand O2 sensor did you use? Haven't heard too many good comments on here about Bosch replacement sensors. Motorcraft seem to work best.

You can't replace any "chip" in the PCM. It's a single non-serviceable unit. And it very seldom, if ever, needs replacing to cure an engine problem.


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.
 

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Discussion Starter · #3 · (Edited)
Bosch and ntk were the brands. I did find a burn on two wires towards the top of the motor leading to the o2 sensor. I cut out the bad wire and butt connected them back. The burned wires were part of the harness, not the o2 sensor. Also, if I disconnect the battery, will that reset the code to see if this worked? Some people are telling me that I have to drive 65 miles before it will reset the code.

:( still showing codes! I thought for sure that was it
 

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Discussion Starter · #4 ·
Is it really likely that those type of sensors would BOTH be bad at the same time brand new? Also, could a vacuum issue cause this? Someone suggested PCV valve or hose.
 

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C2H5OH
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The FSM says to check resistance from the PCM to the O2 connector under the hood.
http://www.filedropper.com/focuso2fault

If you found a couple burnt wires it sounds really likely it's a wiring issue. Corrosion, rust, etc.
There are 2 connections from the O2 to the PCM. The Green/Blue connectors of the O2's, the Grey connector attached to the top of the transmission then it's the PCM connector.
First test from the Grey to the Green and Blue to make sure resistance isn't too high.
 
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