P0135, P0155, P0141, P0161 all at the same time

[Krewat]

It's a 4.6l in my wife's '97 Cougar, but maybe someone here has dealt with a similar issue. She was driving it, SES (check engine) light came on. I read the codes, it came up with a P0155 which is B2S1 O2 sensor heater circuit malfunction (driver's side front). Pulled the connector at the O2 sensor, checked the heater with an ohm meter, got 7 ohms. Supposed to be between 3 and 30, so that checked good. Put it back together, cleared the codes. Drove it for an hour, nothing. Went out the next day, started it up, light came on within 15 seconds. Read the codes. Got all four O2 sensor heater codes, P0135, P0155, P0141, P0161 Cleared them, restarted a few times, two came back, P0135 and P0161. Yes, front passenger side, rear driver's side. Two completely separate wiring harnesses, almost no connection to each other except way up in the power splice. Did it a few more times, each time I read the codes, it's either B1S1, B1S1/B2S2 or all four again. So, subscribe to motorcraftservice.com, get the wiring diagrams, start checking things with an ohm meter. Went all the way to the PCM, pulled the connector, and ohm'd out the O2 sensor heaters. All four heaters check out OK at 7 ohms at the PCM connector. One thing I didn't do was check if there was any resistance to ground, but I will do that in a few minutes. Anyone ever have a situation like this where all four O2 heater codes were coming up? The one thing I notice is in a Ford TSB that it mentions the possible causes, and one of them is "low battery voltage". The battery is not the greatest right now, and was actually boiling over a bit, but cleaned the connections, and it seems to be holding a good charge and not boiling anymore. And, it passed a load test with flying colors. So, I'm basically stuck with checking for resistance to ground, and if that's not it, a new PCM.

[projectSHO89]

My 98 Conturd 2.5 just went through this.

I found the wiring harness for the forward lower O2 harness melted onto the pre-cat.. My own darned fault for not securing it out of the way.

BTW, mine did blow the fuse for the heater circuit. Check yours for the same.... An open will give your all four heater circuit codes.

[Krewat]

Already checked that. EVERYTHING is fine. Even changed the battery today to a known good one.

Still doing it.

Checked front O2's for leakage to ground, found nothing. Will be going out tomorrow to pull every O2 sensor's connector and check everything, including crosstalk between the sensor itself and the heater.

[LxMan1]

If alternator voltage is good, I would start to suspect the PCM as well.

[JJ98]

go with what you think ecu or a bad groun on fire wall ge a friend and move stuff up and down see if you can get it to code out also auto zone got me a ecu for 180 good luck

[Krewat]

Originally Posted by JJ98

go with what you think ecu or a bad groun on fire wall ge a friend and move stuff up and down see if you can get it to code out also auto zone got me a ecu for 180 good luck

I still have to check all the grounds.

Thing is, it doesn't do it right away, it takes a few restarts for it to happen, and it's not always all four, sometimes it's B2S2 and B1S1.

So it's definitely something random. I'll find it, even if I have to open up the PCM myself and repair it

[LxMan1]

You ever get this figured out, Art?

[Krewat]

Originally Posted by LxMan1

You ever get this figured out, Art?

Nope. I've been over everything I can find. All the grounds have been checked.

The one thing I can't yet find is the splice for the +12 to the O2 heaters. The EVTM says it's near a connector near the PCM, but I can't find it. I'll look for it again in another day or two.

After (or if) I check that splice, I am going to see if the PCM is actually energizing the O2 heaters. If it is, good. If it isn't, sounds like the PCM needs to be replaced or repaired. If it is the PCM, I am going to attempt to repair it myself.

I'll definitely post back in this thread with more info when I get it.

[Krewat]

What I've done so far (copied and pasted from my thread at tccoa.com):

Checked all grounds.

Checked and re-checked all connections directly from the PCM connector to the O2 sensor heater circuits and O2 sensor circuits, making sure there were no shorts or even a little bit of resistance between all the different circuits, and ground. Nothing.

I found the green connector near the PCM is the one that goes under the car and feeds the driver's side O2 sensors.

So, I connected directly between the red wire on that green connector (VPWR) and the tan/yellow or white/black wire (both O2 sensor heater circuits for the driver's side), and found:

The PCM is not even TRYING to energize (ground) the heater circuits.

To me, this means the PCM is faulty.

I am going to try this PCM in my sister's '96 t-bird (the one I used to own and sold to her), and see if it gets the same error codes. That will tell me if the PCM itself is bad, or somehow after all the diagnostics, that the vehicle wiring is at fault.

At this point, I am 99.99999% certain that the PCM is not energizing the heater circuits and trying the PCM in my sister's t-bird will just give me that last .00001%

Because the PCM is not even trying to energize the heater circuits, I suspect that a large power transistor (large, because it has to put out at least 6-7 amps) in the PCM is bad, or there is a fuse (or equivalent) on the PCM circuit board that blew.

I can get a PCM off of ebay, but need to get it programmed with the correct calibration (LCJ1 for California emissions, I'm in New York), or even an MBE3 calibration.

I might try the local junkyards and see what I can find.

sousa632, if you need help finding that green connector, and making sure you are checking the correct wires, please, post back here, and we'll work on it together. Again, connect a voltmeter between the tan/yellow or white/black wire in that connector, to the red wire (VPWR or +12). If you get the typical 13-14 volts when running, that means the PCM is not turning on the heaters. I connected the volt meter, started the engine from dead cold, and let it idle for a few minutes, and the MIL (check engine) light came on, all the time watching the volt meter and it never moved. If the PCM was functioning properly, it would ground the tan/yellow and white-black wires, and the volt meter would drop to near zero.

Further, if you disconnect the green connector, and with the volt meter on ohms, on the side of the connector that leads down into the floorboard (not up towards the PCM), check between the tan/yellow and red, and white-black and red, you should see the typical heater circuit resistance which in my car has been anywhere from 6 to 8 ohms depending on outside temperature (it's been bouncing from 40 up to 65 or so here the past week or so).

Also, with the engine running, check with a volt meter between the red wire at that green connector (when it's connected of course), and ground, that you have battery voltage which should be 13-14 volts when running.

[LxMan1]

I had a 94 PCM around here somewhere for a 4.6L Cougar but it had a stuck on injector driver.
Never saw a noid light so bright!!

[Krewat]

From my thread on tccoa.com:

I checked my LCJ1 computer in my sister's '96 t-bird (came with an NPL1) and got the SAME CODES. So yes, it's the computer. ECU. PCM. What-EV-ah!

I have opened the computer, and traced out the four power transistors that control the heater circuits. There are four, so all four are not working at once, which means either the computer is not turning them on, or they have no power. So, I am tracing further, and found a diode that supplies ground to them, but have to find my other ohm-meter to provide enough voltage to actually bias the diode to test it. I will report back after I do that.

[Krewat]

Posted this over at TCCOA.COM:

OK - SUCCESS! I found another computer, code LJC1 locally at my friendly neighborhood junkyard after looking on car-parts.com

$75 + NY sales tax, about $82 later, and VOILA! Problem fixed.

Funny thing, it seems to be running and shifting better than it has in the past 2-3 years. I've only had the new computer in for an hour, and it was all caught up on all monitors (tests) in the first 20 minute drive cycle. Interesting.

Wonder if it had a tune flashed into it before it was junked? Wonder how I could find out? Checksum from a scanner maybe?

Originally Posted by tbirdguy

what is between the microcontroller and mofset?

There is a 24-pin SOIC chip directly driving the MOSFETs. The closest I can find from Motorola/Freescale is this:

http://www.freescale.com/files/analo...et/MC33298.pdf

The outputs are the same pins, but four of the outputs directly drive the MOSFETs, the other four seem to be to "sense" the line from the O2 heaters to the output of the MOSFETs. Which makes sense. That chip also has built-in short detection on it's outputs, so it could conceivably sense whether or not the heater circuit drops in voltage when it's grounded by the MOSFET. Either that, or it's a custom chip that seems to be pretty close. VDD is a different pin (15 instead of 16), but VPWR is in the correct spot. This chip is labeled 71012SE001 and MCA61U01, neither of which I can't find any specs for.

Originally Posted by theterminator93

I'm going to cross check the circuits to be sure there are no shorts, then I suppose I'll be checking the voltage at the connection to the sensors themselves and find out if they're coming on at all. Last resort is yet a third PCM...

Edit: Checked for continuity in the voltage returns from all four heaters and there's continuity between all four of them! I guess I should start looking for shorts, and not the summer clothing kind.

If you check with an OHM meter between each of the heater circuits to another one, at the PCM connector, you will get the resistance on ONE heater (usually around 6-8 ohms) PLUS another one, of another 6-8 ohms. In other words, if I went from one pin of the PCM connector to another, I got around 14 ohms because I was going from one heater, to VPWR, and back on the other heater.

If you check each heater to VPWR, you should see the individual heater at 6-8 ohms (depending on the ambient temperature). If you go from the heater circuit at the PCM connector to GROUND, you will see around 100-200 ohms, because that is feeding back through something in the engine harness most likely, like the MAF, or some other sensor, back to VPWR, and back to the heater circuits again.

The best way is to pull all the O2 sensor connectors, check the O2 sensor heaters there, for both heater circuit leads on the O2 sensor to ground, or the case of the O2 sensor. Then, with all the O2 sensors disconnected, disconnect the PCM, check for shorts between the heater circuits to VPWR and ground - this checks the body harness for shorts or opens, and then plug the O2 sensors back in and check for 6-8 ohms for each heater circuit to VPWR, and that magic high resistance of 100-200 ohms to GROUND. Again, resistance between the heater circuits at the PCM connector to any of the other heater circuits, should be the SUM of two O2 heaters, each at 6-8 ohms, so it should be 12-16 ohms.

[LxMan1]

Glad you got it fixed. The price is fair enough!!

[Krewat]

Yeah, I couldn't complain for $75. Clean looking, and the right code, and it works.

Can't ask for much more