HO2S codes, wiring, and you. (Me).

Silver95bird

Active Member
Joined
Sep 5, 2016
Messages
484
Reaction score
111
Ok, since I bought this 96 GT I have been chasing a heater circuit malfunction code for the front passenger sensor. p0135 . Over time I have now changed the sensor, and unwrapped the harness, and checked the wires for obvious cuts or damage, all the way from the sensor, along the engine, across the front, up behind the PS reservoir, up to the big plug behind the battery. It was pinched pretty bad in a few places (its not the original engine, and these people were hacks, so I take nothing for granted).

There are two wires which split at what look like OEM heat shrinked connections in the first run of the wire. one split is red (power) and the other grey (ground?) for the heater, correct?

Knowing that the drivers aide is working fine, that should mean theres a harness problem with one or both of those heater circuit wires, from the split to the plug at the sensor, right?

I'm at the point of buying a bunch of wire, and running two new lengths of it, unless theres an alternative I'm missing.

The problem is getting worse, causing a p1151 and misfires at 1 and 4 in addition to the heater circuit code, although when driving it, you can tell it does connect at least some of the time, because it will run like poop, the its like flipping a switch and it runs great, until it doesnt. But this isn't good for the car, or my nerves. lol.

Sent from my moto z3 using Tapatalk
 

ttocs

Post Whore
Joined
Oct 9, 2009
Messages
27,926
Reaction score
3,727
Location
Evansville Indiana
any chance it changes conditions (good/bad) with temp? I ask because I have had issues with parts starting to show problems after they got hot and traced it down not to the sensor but to the harness that goes to it. When the motor was hot the harness would expand and loose connection.
 

Silver95bird

Active Member
Joined
Sep 5, 2016
Messages
484
Reaction score
111
Unfortunately it's not that consistent. ive had cold starts that were great, and cold starts where it missed from moment one.
Weather doesn't seem to affect it either.

My best guess is that either one or more spots where it was pinched may have partially cut the wire inside the insulation, or the harness was stretched at some point in the removal/installation of the engine.

Sent from my moto z3 using Tapatalk
 

07GtS197

Well-Known Member
Joined
Mar 16, 2015
Messages
1,776
Reaction score
390
Location
Naples, Fl
That’s a clue right there. If its a cold start it won’t use o2 input. My bet is the fault is elsewhere and the code is the effect not the cause.


Sent from my iPhone using Tapatalk
 

Silver95bird

Active Member
Joined
Sep 5, 2016
Messages
484
Reaction score
111
There may be more than one fault, but the heater circuit malfunction is a hardware fault type code, is it not? either the circuit works, or it doesn't and sets a code?

side note: the replacement sensor I used was a genuine motorcraft sensor, so there should be no issue there.

Sent from my moto z3 using Tapatalk
 

07GtS197

Well-Known Member
Joined
Mar 16, 2015
Messages
1,776
Reaction score
390
Location
Naples, Fl
Yes it is but my point is that it won’t affect drive ability. You can put a meter on the heater circuit and check for 12v on the heater and check the ground for contiuity. If it has 12v at the sensor then either the fault is with the sensor itself or the ground circuit. Try a wiggle test too. But this wouldn’t affect anything except for catalyst effiency after the car goes into closed loop as the sensor and cat won’t be up to the right temp. I don’t see that causing your issue especially if it happens right when the car turns on because it should be in open loop. Maybe the ect or iat are going too so the car never goes into open loop and it’s always using the o2 sensors.


Sent from my iPhone using Tapatalk
 

ttocs

Post Whore
Joined
Oct 9, 2009
Messages
27,926
Reaction score
3,727
Location
Evansville Indiana
The intermitten-ness of this story still leads me to question wire harnesses. Next time it does not start up, go under the hood and just put your hands on as many wire harnesses as you can and just give a tug/pull/push and then try it again and see if it starts. If it does start up then again go under the hood and repeat that process of dicking with harnesses to see if you touch one if it will make the motor run differently.
 

Silver95bird

Active Member
Joined
Sep 5, 2016
Messages
484
Reaction score
111
Well, some progress.
Saturday I had a few minutes, so I replaced the offending 1 and 4 cylinder fuel injectors with spares I haf. Seemed better, but it was hard to tell if it was a partial solution or just dumb luck. still had #4 misfiring.

Today, i took the front Pass side O2 harness off the sensor amd tested it all the way to the connector by the battery. No issues found, low resistance and no apparent breaks found wiggling the harness. Frustrated. Put it all back. started it, still missing.

Removed injector connectors one at a time.
1 2 3 fine, remove 4, no change.
Went to the garage, got a spare coil pack.
Moved the 4 wires over, started it.
Smoother.

Moved the coil onto the bracket, and went for a cruise. much better than its been in ages. still maybe a small miss on 1200 rpm 5th gear bog, but maybe it just needs to clear itself out.

Still no closer to why I'm getting a code for the sensor on the pass side. It has been there since day one, and the new motorcraft sensor put me no closer to an answer. Now i feel confident its not in the lower harness either.

Sent from my moto z3 using Tapatalk
 

RAU03MACH

Well-Known Member
Joined
Apr 23, 2019
Messages
3,219
Reaction score
2,605
Location
NEW MEXICO
Just checking in real quick
It might be the computer
I had a problem like that on a car once changed everything on it
Ordered the computer the code went away
 

Latest posts

Forum statistics

Threads
74,993
Messages
1,454,234
Members
13,628
Latest member
reedj304

Members online

Top