CEL and codes

[Overdrive]

Hey, everyone. I just recently got my IMS retrofit and RMS fixed at a great independent Porsche shop here in CT, but a few days before I planned to drop the car there, the CEL came on.

This is the first time the light has ever come on in my year of ownership, with only about 2500 miles on it in that period of time. The car wasn't making any terrible noises or anything, the light simply came on at the end of my morning commute to work. I turned into the parking lot and the light came on about 2 seconds after that. So I had the shop come and pick up the car early and hold it at their shop until it was scheduled to be worked on.

When they began to work on the car they did a diagnostic for the CEL and were getting codes indicating a vacuum leak, and informed me that they suspected it could be a bad MAF rather than an actual leak. They did a leak test and found no leaks. Next they cleaned the MAF, cleared the light, and drove the car for at least a 40 mile commute, round trip. The light did not return and they finished the job for the IMS, RMS, rebalanced my tires which got rid of my steering shake, and I had them do my oil change since it was due anyways. They said if the light returned it may be a bad MAF and to replace that. The car ran great after getting it back, felt smoother than before (MOTUL oil must really be that good), but after driving home, parking, and then hopping in again after a short time to go to the local dealer to make a spare key, the light came back on.

I recently bought a MAF and air filter from PelicanParts and dropped them in yesterday. The MAF, at least the part that was in the hose and not out in the engine bay, was completely clean, but I remebered they'd just cleaned it at the shop, so I had to disregard its condition. Borrowing my friend's scanner, I cleared the codes after the installs and took the car on a good uneventful 80 mile drive over the next few hours. I parked at a Dunkin Donuts, ate some food for about a half hour at most, hopped back in and drove to the college campus down the road. I parked, and after about a minute of just idling, the light came back on.

So here are the codes I got after scanning it again:

P1117: Engine Coolant Sensor
P1121:: Throttle Position Sensor inconsistent with MAF
P1124: Throttle Position Sensor out of range
P0140: O2 sensor Bank 1, sensor 2

Prior to the MAF and air filter there were 6 codes, which I neglected to write down, and this time there were only 4, but I'm pretty positive they're 4 of the same from the original 6, so maybe there are multiple issues and the MAF replacement was still necessary.

I have not checked the coolant yet, as I just pulled up these codes today, but if anyone can provide some insight and troubleshooting recommendations, that'd be greatly appreciated. I'm not about to start throwing parts at the problem. Thanks in advance, and thanks for taking the time to read.

[Johnny Danger]

None of those codes really pertain to the MAF sensor. Why did your "indy" advise you otherwise ?

[Jager]

My Bentley book shows the P1117 alarm as a pre-catalyst O2 sensor cyl 1-3 heating alarm, how did you come up with a coolant alarm?

Throttle position alarms might be throttle position adaptation - Was the battery disconnected recently?

Your 0140 is post-catalyst O2 sensor alarm, could be loose connection. I would try cleaning the connector first. If that does not work swap with the other bank, this will tell you a lot.

[Overdrive]

Ok, reply time.

Danger: I honestly could not tell you what codes my indy pulled while he was working on it, though I may call him and see if he has them documented. What he told me was that the codes he was getting were indicating that the car was running lean, which led him down the path of finding a vacuum leak or seeing if the MAF was dirty and therefore sensing a leak when there wasn't one. Since the light hadn't come back on after he cleaned the MAF, he told me if it does come back on then the MAF likely needed replacing. I think it may have just not been driven quite far enough for the light to cycle back on. I was just listing the codes that I got after replacing the air filter and MAF and resetting the light this weekend.

Jager: Until I get my hands on a Bentley manual, I'll just have to live off of you guys and internet searching. My search for the P1117 brought up that coolant one, but I'm going to go by what you found in the book.

Yes, the battery was disconnected recently. It was done once at the shop while the car was getting the IMSR if I remember correctly, since the trip meter was at a lower mileage than when I left it and the clock was off time. It was disconnected again a few days later while the top was getting replaced, again because when I took the car back the trip meter was low and the clock was way off.

Thanks for the advice on the last code, I'll have to see what happens there. Hopefully I can get the car squared away before summer's out.

[Johnny Danger]

This link maybe helpful for you in the future .

http://www.iwantaporsche.net/BoxsterCheckEngineLightCodes.htm

[Overdrive]

Thanks, Johnny. So using that listing from Randall, here's what the codes I pulled note:

P1117 Oxygen Sensor Heating 1 After Catalytic Converter - Below Lower Limit

P1121 Oxygen Sensor Heating 2 After Catalytic Converter - Below Lower Limit

P1124 Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Rich Threshold

P0140 Oxygen Sensor After Catalytic Converter (cylinders 1 - 3) - Interruption of Signal

So if I'm understanding this right, it all seems to be on the 1-3 side of the engine. That "Rich Threshold " code has me wondering, though. Is it reading rich because the other side is reading lean? Either way, aside from checking that the connection isn't just loose on one of the sensors, what could I be looking at here?

[Jager]

What is the history of your AOS? Have you opened the oil fill cap while the car is running recently? After you remove the oil fill cap does the engine idle go up or down?

You could try swapping O2 sensors, left with right side, and clear the codes. This will provide some information.

[Overdrive]

Jager, the best answer I can give you regarding the AOS history is unknown. It has not been replaced in my year of ownership, and I wouldn't be surprised if it's the original unit on the car. Prior to my purchase, it was crashed, bought at auction as a repairable collision, repaired, driven as the personal car for about 4 years of the owner of the shop that fixed it, and then sat on his shop's lot for about 5 years until I bought it. From 97-05 the car had managed to accumulate 40k in mileage.

Here's the car's history since I've had it:
- Ignition Switch replaced (June 2010)
- Michelin PilotSport A/S Plus set put on last year (Fall 2010)
- Alternator and belt replaced (June 2011)
- Battery replaced (June 2011)
- IMSR and RMS (June 2011)
- Oil change (June 2011)
- Robbins glass window top (July 2011)
- Air filter and MAF replaced (July 2011)

Other than that I am simply assuming that everything else on the car that has gone untouched is original. The car was as stock as could be and now only isn't because of the new top, so it wouldn't surprise me if the majority of parts in that car are from 1997.

[Topless]

Clear the codes and see if they come back. I had a similar issue with oddball error codes after replacing my battery. When voltage to the DME went to zero it caused a hickup . I cleared them and they did not return.

Since your car was damaged in an accident it may also be a damaged sensor harness or DME harness. You can trace the wires and see if there are any chaff points or loose connectors.

[Overdrive]

I am wondering if maybe the throttle position codes have to do with the car relearning after the battery got disconnected, but it's had a good few hundred miles put on it since then, and about 90 miles since the MAF replacement and clearing of the codes at that time.

If I swap banks with the O2 sensors, should I clear the codes or simply scan and see if the error switches sides? Just want to know if I should set time aside for another near 100 mile drive to bring the codes back up.

[Jager]

You will have to clear the codes after swapping the O2 sensors, then see what happens after a few miles.

[Overdrive]

Ok, time for a bit of an update.

Haven't done any 02 bank swapping, but did use the code reader again to reset the light and see if it comes back. This time I'm reading 8 codes, some being repeats from before, but here they are:


P1117 Oxygen Sensor Heating 1 After Catalytic Converter - Below Lower Limit

P1121 Oxygen Sensor Heating 2 After Catalytic Converter - Below Lower Limit

P1124 Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Rich Threshold

P0140 Oxygen Sensor After Catalytic Converter (cylinders 1 - 3) - Interruption of Signal

P0410 Secondary Air Injection System - Signal Implausible (Cylinders 1-3)

P1126 Oxygen Sensing Adaptation Area 1 (Cylinders 4-6) - Rich Threshold

P1411 Secondary Air Injection System - Signal Implausible (Cylinders 4-6)

P0160 Oxygen Sensor After Catalytic Converter (Cylinders 4-6) - Interruption of Signal

[mikefocke]

the MAF revision wasn't the same as the ECU flash expected.

there is a loose connection from the wiring harness to the ECU.

I'm assuming everything is stock?

[Overdrive]

Yes, Mike, the car's 100% stock (if you exclude my having to replace the top), and the only modification has been an IMS retrofit and RMS replacement. I listed all work done to date a few posts earlier in this thread.

How should I go about tackling the harness issue? Just go find it and make sure it's all snug and plugged or does it require full replacement? Any chance this loose connection might also be causing the flickering/dimming of all of my car's lights (interior & exterior) and cutting out of stereo sound while running? The ignition switch has been replaced with no change in the symptoms.

[Overdrive]

Update: The CEL came back on very quickly yesterday after the reset, within a few hours and maybe about 20 miles or less of driving. Only 6 of the 8 codes came back up, and I believe it was 1126 and 0410 that did not come back.

[Topless]

You are getting a bucketload of random error codes that point to:
Damaged harness or bad connections, damaged DME, bad ground connection at battery or DME. When the trans came out did something get pinched?

Your DME is pretty aggravated right now and not giving much meaningful info to help eliminate all the possibilities.

[Overdrive]

Well Topless, the CEL was on before the IMS work was done, so while I don't know that these same codes were the ones that arose when it originally came on, they are what have been continually coming up. The shop owner did mention that the electrical issues I've been experiencing could be due to a bad harness or problem within the harness, so maybe this is the culprit after all.

But just so I'm not confusing myself, are we talking about the main harness for the vehicle or the individual harnesses on the O2 sensors...or both?

[Topless]

You have discovered four different sets of error codes that are not likely to be related: Throttle pos sensor, coolant sensor, secondary air inj., and O2 sensors.

P1117: Engine Coolant Sensor
P1121:: Throttle Position Sensor inconsistent with MAF
P1124: Throttle Position Sensor out of range
P0140: O2 sensor Bank 1, sensor 2

P1117 Oxygen Sensor Heating 1 After Catalytic Converter - Below Lower Limit

P1121 Oxygen Sensor Heating 2 After Catalytic Converter - Below Lower Limit

P1124 Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Rich Threshold

P0140 Oxygen Sensor After Catalytic Converter (cylinders 1 - 3) - Interruption of Signal

P0410 Secondary Air Injection System - Signal Implausible (Cylinders 1-3)

P1126 Oxygen Sensing Adaptation Area 1 (Cylinders 4-6) - Rich Threshold

P1411 Secondary Air Injection System - Signal Implausible (Cylinders 4-6)

P0160 Oxygen Sensor After Catalytic Converter (Cylinders 4-6) - Interruption of Signal


There is very little common ground here which is why it looks more like random codes from a damaged DME or harness. It could be as simple as a poor battery ground connection or ign. switch issue. If it were my car I would start at the DME and follow the harness wire looms as they branch off looking for rodent/water damage, chafe, fouled connectors etc. I would look hard at everything that was changed out just prior the the flurry of error codes. I would re-trace my steps to see if I forgot something or fouled it up. It happens.

"Interruption of Signal" is a big clue and usually means a bad connection.

[Overdrive]

just to clarify, that first set of 4 codes that you quoted was me looking up the codes from a general listing. Everything afterward is after I was directed by members here to a listing of the codes that is Porsche specific, so you can see how P1117 for the rest of the world and P1117 for Porsche are two very different things.

But I definitely get what you're saying regarding "interruption of signal". Guess it may be time to start tracing wires and connections...oh joy.

I do want to check the grounds myself, and particularly that grounding strap on the alternator. I've been told by two different technicians that they looked fine, but I want to be sure, and then start looking at what's likely to be a lot of 15 year old wiring. I'll also take a look at the ignition switch to be sure it was done right.

[Topless]

Yes, those Ford code descriptions are probably not very useful here.

"Interruption of signal, sensor heating below limit, and signal implausible" point to bad connections from O2 sensors on both banks and secondary air injection. I would ignore the mixture codes "rich threshold" until you have solved the connection problems.