2001 Ford Escort Troble code P0135

CBANDAK

MEMBER
2001 FORD ESCORT
2.0L
4 CYL
FWD
AUTOMATIC
150,000 MILES

I have been getting trouble code p0135. I have done most of the fixes that I have found discussed on forums. So far I have done the following:
Replaced the O2 sensor (twice under warranty)
Replaced the connector/pigtail
Checked and confirmed conductivity of wires
Checked and confirmed resistance of o2 sensor
Checked and confirmed fuses

The only other possible problems that I can find listed on forums are a damaged PCM and/or damaged temperature sensor module. Based on the temperature gauge functioning properly in the dash, I have ruled that out as a possibility. It's looking like replacing the PCM is my next best option. I believe this is viable because as soon as I turn on the car after having cleared the codes via OBDII, the MIL indicator comes on within a few minutes. This is without driving the car anywhere and just running in place.

In your opinion, is this the next fix to be done or am I missing a step? And if replacing the PCM, does this year/model have to have the PCM flashed? And must I take it to the dealership to have that done or can I flash it at home? PLEASE HELP.

1 Reply

HMAC300

MECHANIC
48,601 POSTS

Here is how to test for a bad pcm or not
32) Check VPWR Voltage To HO2S HOTA Circuit Harness Connector
Turn ignition switch to OFF position. Disconnect suspect HO2S harness connector. Inspect wiring harness for damage and repair as necessary. Turn ignition switch to ON position. Using a DVOM, measure voltage between suspect HO2S harness connector SIG RTN and VPWR terminals. See Fig. 68 or Fig. 69. If voltage is more than 10.5 volts, go to next step. If voltage is 10.5 volts or less, on LS models go to TEST B, step 5). On all other models, check VPWR circuit fuse. Replace as necessary. If VPWR circuit fuse is okay, repair open in VPWR circuit. See WIRING DIAGRAMS article.
33) Check HO2S HOTA Circuit For Short To GND Or VPWR

Turn ignition switch to OFF position. Disconnect scan tool from DLC. Disconnect PCM connector (s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance between PCM harness connector suspect HO2S HOTA circuit terminal and PWR GND terminal. See PCM HO2S, VPWR & GROUND TERMINAL IDENTIFICATION. See Fig. 68 or Fig. 69. Using a DVOM, measure resistance between suspect HO2S harness connector HO2S HOTA terminal and SIG RTN and VPWR terminals. If all resistance measurements are more than 10 k/ohms, go to next step. If any resistance measurement is 10 k/ohms or less, repair short in affected circuit.
34) Check HO2S HOTA Circuit For Open

Leave ignition switch turned to OFF position and HO2S disconnected. Using a DVOM, measure resistance of suspect HO2S HOTA circuit between PCM harness connector terminal and suspect HO2S harness connector terminal. See PCM HO2S, VPWR & GROUND TERMINAL IDENTIFICATION table. See Fig. 68 or Fig. 69. If resistance is 5 ohms or more, repair open circuit or excessive resistance in HOTA circuit. If resistance is less than 5 ohms, go to next step.
35) Check HO2S HOTA Resistance
you have to measure resistance not conductivity although it may show ok. And this is o2 sensor before converter.

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