Help! 2000 Accord EX 4cyl. Does anyone know if insulation removed from three of four harness wires leading to primary O2 sensor can cause code 0135 (heater circuit fault)? New sensor installed then discovered partially bare wires (someone probably tried to test circuit). Rebuilt ECM installed too. Old ECM showed 1149, 1164, 1165 & 1167 (all relate to O2 circuit) at one time or another. I inspected bare wires closely and don't see any damage. However, a Honda parts man and a mechanic told me that corrosion (even though not visable) could cause the problem. Could shrink tape solve the problem? How about if I cut and splice the wires? How can I remove corrosion (baking soda, vinegar, what works?)? How hard to change wire harness? Does it run direct from sensor to ECM (is it one piece)? Anyone know the purpose of each of the four wires? If you can answer any parts of this it would be greatly appreciated. Please indicate how confident you are in your response(10 - absolutely, positively, guaranteed and 1 - just a guess). It will be such a relief if I can resolve this. If I bring it to Honda they will probably want to replace the engine.

 

P0135 is for the heater circuit (front sensor near radiator).

Seems to me that you should try to properly insulate the wires & check they're not grounded anywhere, corrosion, loose plugs, etc...?

 

Thanks Jim.
Checked connections and grounding and no visable corrosion. I'll try to better insulate them with shrink tape.

 

There are two circuits that have two wires each on and O2 sensor.

One runs current through the O2 sensor to heat it up (heater circuit) so it can adjust the fuel mixture quicker (emissions requirement). The other two are the signal part of the circuit that the ECU reads.

Your problem could be the wiring, or the sensor. Since you know it is the heater circuit, test the resistance across the two pins on the sensor that have the same wire color. The pic is from an acura tsx manual, but it should be the same. The resistance should be 2.1-2.9 ohms.

There are also fuses that could be blown. In the acura manual #19 (40a) in the fuse box under the hood. #4 (A/F sensor, 15A) and #23 (IGP, 7.5A). Your fuses may be numbered or labeled differently, but definitely try to find them.