Multiple Codes - Ground problem again?

[lefty]

On my 2002 2.5 (76K), a couple of weeks ago I got a CEL and a P1195 - EGR boost sensor circuit malfunction. Before worrying about trying to clean it, I checked the connections, cleared the code, and it did not return.

Today the CEL comes back on, and I expected to see the P1195 again. But no. Instead, I had 4 codes, none of which were P1195:

P0100 - Mass-airflow (MAF) sensor circuit malfunction
P0110 - Intake air temperature (IAT) [air filter box] sensor circuit malfunction
P0115 - Engine coolant temperature (ECT) sensor circuit malfunction
P0120 - Throttle position sensor (TPS) circuit malfunction

There was some Freeze Frame data on the reader, among which two indicated the car was not moving at the time and the rpm was 630.

The only other things of note was that I let the engine idle for a good 10 min. or so after starting it the day before (dealing with a family problem), and the CEL at times today went off and then on, coupled with a slight lag or buck in the engine, while at at a low speed/rpm (once while backing up the driveway). Otherwise, car seems to be running just fine.

I can't believe all these circuits are failing (odd that they are so closely grouped in number, too), and I suspect that I have another ground problem triggering all these. That was the problem I had about a year ago, when I had several simultaneous transaxle solenoid codes. saint suggested a ground problem, randy pointed out where the likely problem was (one of those flat molex plugs), and refreshing those grounds (on the transaxle housing) was the end of it.

My engine does have an oxidized look to it (somewhat frosty aluminum valve covers, etc.), so I suspect there is another place with the same kind of grounding problem. I'm going to pursue that, but if my account above rings any other kind of bells with anyone, I'd appreciate knowing. I can also post more of the Freeze Frame data if it is useful. Thanks.

[yel-low]

I once had this same succession of error codes come up on my 2.5. You are correct that they stem from a common issue. I believe (has been many years) that my issued started after an engine swap/heavy engine work and I left something unplugged or had a torn intake boot. I really wish I could remember what it was that actually triggered all the codes all of a sudden but my memory fails.

The main harness that connects all those sensors runs along the rear end of the intake manifold and loops around the left and right side of the engine. Its worth a shot tracing it and seeing if anything odd is up. The metal bracket on the rear of the manifold grounds some tabs on the solenoids. This is also a suspect spot. I would try unbolting the entire bracket and cleaning things up a bit. Sorry for not shedding a bit more help.

[lefty]

thanks, randy. i'll trace out that harness and the connections, looking for something loose or oxidized, especially that bracket. it makes sense that it is something like that. thanks for posting.

[bigb]

+1 for a connector.

hopefully it's something as simple as that. let us know

[lefty]

I hope so, bigb. I drove around this am before I had a chance to look under the hood, and she stalled a few different times at idle. At noon I worked all the connectors I saw along and near the back part of the harness, cleared all the codes, and she has behaved normally since (no codes, no CEL, no stalls).

I could not do more yet (but I will) because I had a cracked molar extracted in the early afternoon, and I am laying low at the moment. To add insult to injury, instructions say I can't mix alcohol with the surgery and meds. Is that really true ? Bummer, as we used to say. Waiting for that second dose of percocet...

[bigb]

so in the 2.3 these 3 are all on the same harness.

P0100 - Mass-airflow (MAF) sensor circuit malfunction
P0110 - Intake air temperature (IAT) [ air filter box] sensor circuit malfunction
P0120 - Throttle position sensor (TPS) circuit malfunction

For the coolant temp sensor (P0115) I'm not sure on the 2.5 where this sensor is but on the 2.3 it is on the rear left side of the engine near the power steering pump. on top of that it only has one connector similar to the oil pressure sensor (idiot light). meaning it uses the engine to ground the signal.


so... with that being said, as your post title implies, check the engine grounding. it might not be a connector, but the main ground strap itself. I base this from the engine temp sensor code alone since it cannot possibly be the connector (unless it is in a different place on the 2.5). I guess one of the 2.5 guru's can comment on that.

[yel-low]

There are two engine temp sensors on the 2.5. Both are within 1" of each other. They are located on the belt side of the engine right next to the filler neck. The both have single wire connectors on them.

[lefty]

Continued quiet here.

Pulled some more connectors on the harness this morning; pristine inside. Those connectors are a good design; they almost pop open like a cork on a wine bottle.

The temp sensors have single wires entering them, as randy said, and are by their lonesome. There doesn't seem much to do about them.

Looked at the two ground straps coming off the neg battery terminal. both are oxidized a bit. Unbolted the top one, which goes next to the diagnostics port, above the firewall on the driver's side, and refreshed it. It had some but minor corrosion. The lower one, low behind the engine toward the firewall, wasn't so easy to get at from above and get a purchase on the bolt, but looks like it might need some attention. After dropping a box end into the undercarriage while trying to get at it (did fish it out), decided the undercarriage might need to come off to get at that one properly.

Hope to get to the bracket bolts behind the intake manifold tomorrow.

Anyway, no more codes or CEL or stalls today.

Thanks for the advice, guys.

[lefty]

I did get to the rear harness bracket and that metal plate bracket near the EGR. The bolts look a little corroded on the outside, but show fresh metal when taken off.

Poking around the harness surrounding the intake manifold, I did see one of those flat white molex plugs under the intake boot, bolted to the engine, and I did not like the way it looked. I'm pretty sure it is the JC-05 ground point (ground points image below), and does ground at least a few of the things I got codes on. The intake boot will have to come off to fully get at this plug without damaging it, but for the time being I did get a box end on the 10 mm bolt on the tab and worked it a bit.

I ran her around after that, and the continued good news is that no more codes or other issues have shown up. I'm going to let this post rest. Thanks randy and bigb for your advice, and happy new year to all.

http://img851.imageshack.us/img851/4376/klgrounds.jpg

[bigb]

for completeness of discussion, the 2.3 also has 2 temps sensors for the engine.

I believe one goes to the ECU and the second is for the dashboard meter.

actually, this is an interesting note since your dash sensor could work but the one for the ECU could be off and you would never know

now that I think of that I think I'm going to OHM them both next time I'm in the neighbourhood