2005 LS v6 - Misfire -> CAT -> TPS ?

[jbk23]

Hi everybody. This forum has been very helpful so far, but now I'm at a loss. I figured I'd post here before I take it to the dealer...

My problems started with a misfire. I think that led to my CAT going bad. I'm pretty sure I will have to replace the CAT eventually, but wanted to make sure everything else was fixed before spending cash on it. It should be noted all of my problems started after/during medium to heavy rains. I didn't put 2 and 2 together until February/March. It was pretty clear water leaks through the windshield wiper mount point. I swapped the O2 sensors between bank1 and bank2 to determine if the O2 sensors had gone bad or the CAT. Now I'm getting some error codes that seem to point to the throttle position sensor (TPS) going bad. I have swapped that out, but am still having problems.

Nov 2009 - ~104k
Code P0306 - Misfire spark plug #6.
Changed all 6 spark plugs, moved COP from #6 to #5 to diagnose

Dec 2009 - ~104.5k
Code P0305 - Misfire spark plug #5.
Replaced #5 COP with new COP

Jan 2010 - ~105k
Code P0430 - Catalytic converter operating below threshold (bank2)
Swapped O2 sensors between bank1 and bank2 - cleared codes
Code P0430 - CAT still operating below threshold (bank2) -- still active
Purchased 4 new O2 sensors (not installed)

Mar 2010 - ~105.5k
Code P0306 - Misfire spark plug #6.
Some clear water detected in spark plug wells 4-6. Used air compressor to clear it
Replaced #6 COP.


Apr 2010 - ~106k
Determined water was leaking from windshield wiper mount point into wells #4-#6
Added a diverter to keep rain water from getting into spark plug wells from the windshield wiper mount point


May 2010 - ~106.5k
Car starting going into LHM, codes P2107 and P2110
No water found in spark plug wells. COP 6 seemed okay. No misfire codes
Replaced Throttle Position Sensor (TPS)
New codes, P0122 P0222 P0223, in addition to previous codes, pointing to voltage problems with the TPS.


Current Active OBD2 codes(cleared manually 5/12, but likely to return)

• P0122 - Throttle/Pedal Position Sensor/Switch A Circuit Low Input
• P0222 - Throttle/Pedal Position Sensor/Switch B Circuit Low Input
• P0223 - Throttle/Pedal Position Sensor/Switch B Circuit High Input
• P0430 - Catalyst System Efficiency Below Threshold (Bank 2)
• P2107 - Throttle Actuator Control Motor Processor Malfunction
• P2110 - Throttle Actuator Control System - Forced Limited RPM (LHM)

Other codes that had appeared within the past month before TPS swap:

• P2104 - Throttle Actuator Control System - Forced Idle Mode
• P2112 - Throttle Actuator Control System - Stuck Closed

I have kept the car below 2500 rpms for the past 2 days and haven't had the car go into LHM. I'm pretty confident next time I get on the gas it will go into LHM soon after. Any ideas what to try next? I read before about getting a new battery as this one has the original, but i don't have any other electrical problems.

Thanks!
Josh

[shorod]

Consider that your battery is not around 5 years old though and likely very near the end of its service life. It won't be long before you'll be investing in a new battery anyway, may as well change it now before it leaves you stranded. Worst case you avoid a towing bill in the future but still don't fix the other issues.

I have the factory service manual for the 2002 model year and unfortunately it won't have much for diagnostics of the electronic throttle body. You might consider a service like AlldataDIY that will give you access to the full factory service manual information for your car, including the diagnostic flow diagrams for an annual fee.

-Rod

[jbk23]

Thanks Rod. I have read your comments in other threads and you've been a big help.

I started up the car after work and immediately it went into LHM. I checked the codes and it had P2107 and P2110, along with P0430 which it has had for the past several months. I went and had the battery tested at Autozone. It tested at 100% and the green light was on inside the battery. I was kind of hesitant to replace it after the test.

I had already made an appointment to take it to the dealer tomorrow morning for a diagnosis at least. I will post what I find out.

Josh

[joegr]

2003 and early 2004 have some throttle body problems. All of the 2005 and 2006 that I have heard of with the codes that you call out were due to marginal COPs (Coil On Plug) causing electrical noise that confused the PCM. The sure solution to the problem is to replace the other five coils.

Just to be clear here: Misfires from the coils often cause false throttle body and gas pedal failure codes. These false codes cause the PCM to go into limp mode. This is true even if no misfire codes come up. The misfire has to be pretty bad to set a code, but a slight misfire can cause the false throttle body codes.

[joegr]

Posting problems...

[jbk23]

Thanks Joegr. I saw your reply last night, but ended up dropping it off at the dealer anyway this morning. After discussing my history, the first thing he said was that they recommend replacing all the coils after a misfire. Just because of the RF noise that gets in the system...

I left it there for them to diagnose for sure just because I'd like to get their opinion after checking it out. At this point I think I might end up replacing all 6 COPs just to clear it out. Hopefully it isn't too much for them to do that, because I don't want to deal with removing the manifold again.

[jbk23]

Okay service technician recommendation. I didn't talk to the tech directly but one of the service managers.

Replace 4 remaining original coils and all 6 spark plugs. Service manager thought he put change the spark plugs because they weren't motorcraft plugs. I had written down that I had changed all 6 plugs in Decemeber. I think he knew that, but couldn't tell for sure. Service manager didn't seem concerned about replacing the 2 coils that I have already replaced. I bought 1 today on my way home from Autozone and thought I'd replace coil #4 this weekend. Not sure when I will get to tackling COPs 1-3. Should I do them all at the same time since I have already changed 2 of the 6?

He said the error codes were coming from the throttle body, not from the throttle position sensor. He knew I had just changed the throttle position sensor. Looked that up online and found one used for $155. Didn't find any new on a quick search. Quoted the part at $241. Didn't look too complicated, just bolts off and on from first glance.

Said rarely honeycombs in the CAT will clear out, but only if it's slightly damaged. He thinks it needs replaced too.

I declined having any work done. Fortunately I had a coupon for a free diagnostic of a check engine light from them. Saved me $107.

[joegr]

Change out all the remaining coils, and change the plugs too if they aren't OEM. The LS does not like non-OEM plugs at all. Do this before you do anything to the throttle body. You may find that you don't really have a problem with it.
Your catalytic converters will probably have to be replaced, but you should wait to do that until you are sure that all the other problems are taken care of.

[shorod]

I totally agree with joegr above. Change the coils and plugs. I've had good luck with NGK Iridium plugs in both a V6 and a V8 LS (as well as several other modern vehicles), but several others don't suggest anything but OEM.

O'Reilly Auto Parts has pretty good prices on the coil packs and when I purchased mine from there they came in a BWD box but had Motorcraft stickers on them with Motorcraft part numbers.

-Rod

[jbk23]

Thanks guys for the replys. I bought a new coil from Autozone Friday afternoon. I've bought the other 2 coils from Autozone as well, Duralast brand. I swapped out #4 original coil with the new one Saturday morning. So 4, 5, and 6 all have replacement Duralast coils. That is the same side where the CAT error code appears. So far I haven't had any error codes besides the P0430. I'm not confident I'm out of the woods yet though, but the car seems to be running fine. I also took off the throttle bottle and did a visual inspection. The dealer said the sensor is inside of it anyway, but I thought I'd take a look. The throttle body gasket looked fine as well.

I think my plan is to pull the trigger on ordering 6 new plugs and 3 new coils at the next sign of trouble. I'll need to plan a time where I can have somebody help me on it too. Thanks for the tip on a place to order parts. I've found some good prices at Rock Auto as well. I'll post back on how it goes this week. Thanks again for your replies guys!