[kingsly]

Hey y'all, my '00 4.0 has been exhibiting some very weird emissions/code behavior:

P0135/0155
Went through a handful of O2 sensors before I got a pair that worked (DIY writeup coming soon). The new sensors switched like a charm in the live graph and both fuel systems gloriously went closed loop for the first time in months. :thumb:
However I cannot get this persistent 02 heater circuit bank 1/2 sensor 1 code to go away. It's two white wires and a resistive element - not sure what could possibly be wrong. The ETM implies that they're powered through the Ignition coil relay - but doesn't specify where that is to be found (my brain turns to mush when reading the ETM so that doesn't help...).

IF it's a bad relay that totally makes sense that it would theoretically also cause:

P1300/0303/0306/0307/0308
A whole lotta misfires! Plus random multi misfire. Cyls' 3,6,7 & 8 so doesn't sound too likely it's a single coil gone bad. Dual coil failure? 4x wire failure???

The CEL flashes occasionally, usually under load at freeway speeds - hitting a big hill for instance. Never does it in city driving. Oddly there's no noticeable difference in engine performance weather it's flashing (misfiring?) or not. Runs smooth, seems to pull fine if I mash the throttle, etc. Never once felt the classic misfire roughness or even the slightest shimmy.

And that's the mystery.

Help?

 

[Jos Geuze]

Hi

The ETM clearly displays the feed to the oxygen sensors through fuse F26 in the section A1 multiport fuel injection. This fuse is located after the Ignition relay. The lines that are marked with the number 15 are the wires fed through this relay RL15. The relay itself can be found under the power distribution Y1. The relay is used for so many applications that you can rule out this to be faulty. If it is broken you can not start the car.

Misfires can be caused by faulty sensors or connector to the sensor. This connector is fitted very close to the exhaust and turnes brittle over time. If you have misfires you will feel that there is loss of power so I would look to the sensors and connectors first.

Best regards

Jos

 

[kingsly]

Thanks Jos, I'll check out the sensors. Just because I could, I went ahead and swapped RL15 and the CEL came back after about a mile - as you said it was not likely that was the problem anyway.

It stands to reason if the engine were truly misfiring, I'd be feeling it right? I don't get why it's only under load conditions - the freeze frame data for P0303 shows load % at 29.4, both banks CL, and coolant temps at 93ºC

 

[kingsly]

Checking in on this thread since I'm still chasing the code. The blinking light seems more and more common - almost always under high manifold pressure conditions: hill climbs where there's a lot of throttle but not gaining much speed, etc. but NO actual symptoms of misfire. Engine is smooth as it always is.

I'm stumped.

 

[samer0214]

Kingsly: I'm having the same issues as you are with the following codes:P1314/1313/0300/0303. I replaced the coil pack for cylinders 2 & 3 to no avail. Still the same issues, and to think if it were the coil pack, I should also be getting a P0302 (since it's the same pack), but I'm not.

I've replaced the spark plugs and installed new 8mm wires, with no change. I am at a loss as to what to do next. I have not replaced any O2 sensors. I notice from your original post that you have some experience with interpreting Fuel Maps, which I can capture with my Nanocom but have no clue how to interpret.

Did you ever solve your CEL issue?