NEED HELP P1514 TAC System MAF Performance

darsch

Active Member
I've got a crazy issue that started this week that hopefully you guys can help me figure out but first some history and vehicle details.
2002 Bravada 280000kms, 4.2L inline 6
I've had the truck for ten years and for many years I've had an off-idle hesitation that sometimes stalls the engine when trying to accelerate from a stop.
Early last spring I had the tranny rebuilt, then did a good tune-up which includes:
fuel filter, MAP sensor, camshaft position actuator valve, air temp sensor, spark plugs, front oxygen sensor, air filter. Removed the throttle body and cleaned it real good which got rid of the hesitation. Tried replacing the camshaft position sensor but two aftermarket ones didn't work so I haven't tried another one since. I did remove the throttle body again last fall but it was still nice and clean so I didn't do anything to it.
A month later the new torque converter failed and took out the whole guts of the tranny so in it went again on warranty. When I got it back the hesitation was back. Been the same since.
On Tuesday going at 100km/h with cruise on, the engine suddenly died, pulled onto the shoulder, put it in park, turned the ignition off, restarted perfectly with engine light on. The hesitation is now gone and have full power again. Got to a parking lot and checked the code and it said P1514 TAC System MAF Performance. Cleared the code and drove home with no problems.
Next drive today at 50km/h and engine dies. Stopped, put in park, turned off ignition, went to start it but was in limp mode at 500rpm and engine idled extremely rough. Got same code again, cleared it but took about five minutes before it started and ran fine. Drove about a mile and it died again. Coasted into a parking lot, restarted rough, tried again and ran fine but the hesitation was back. Got an hour down the highway and died again, put it in neutral, shut off the ignition as far as I could, restarted fine, put back in gear and kept going. Cruise control wouldn't work until fifteen minutes later, not sure about hesitation. Went another half hour on highway and died again but would not restart, had to pull over and stop for about five minutes before I could get the engine to start normally again, no hesitation, full power. Made it home and then cleared the code again.

So since this doesn't really have a MAF sensor that is cleanable would I be looking at a new throttle body? Should I try a sensor reset like one of you suggested in another post by disconnecting the battery and touching the cables together for a minute?

Thanks.
 

Mooseman

Moderator
Reading on the P1514 gives this as possible causes:

-Faulty Throttle Actuator Control (TAC)
-Throttle Actuator Control (TAC) harness is open or shorted
-Throttle Actuator Control (TAC) circuit poor electrical connection
-Faulty Mass Air Flow (MAF) Sensor

Since playing with the wiring and it's intermittent nature, sounds like a wiring issue, specifically wires from the PCM to the throttle body. It can't be the MAF since you don't have one. It could also be a failing throttle body but the wiring should be checked out thoroughly. If you have another throttle body or can get one cheap in a yard, you could swap it out as a quick test.
 
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darsch

Active Member
It never died going over bumps but I will play around with the wiring this afternoon and see if I can find a loose connection somewhere plus call around and find a used throttle body.
 
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darsch

Active Member
I've got a can of MAF Sensor Clean and was curious if this is safe to spray onto the electrical connections? Thinking of making sure the PCM and throttle body wire connections are clean.
I also found a used throttle body and a PCM for $150 each with 135000kms on it.
 

Mooseman

Moderator
MAF cleaner should be OK since it is used to clean wire thin sensitive sensors. If you swap the PCM, you'll have to do a security relearn. A search for the procedure should bring it up.

$150 each? I think that's expensive, especially for the TB although I'm going on U-Pull prices.
 

AtlWrk

Well-Known Member
Before shelling out for replacement parts, rule out the easy stuff first. Throttle bodies are pretty robust--they do fail (albeit it very rarely) but it's usually a mechanical problem like jamming or the sensor circuits going. Neither of these match your symptoms and you'd have different DTCs.

My money is still on a problem with the wires at the throttle body connector or the connector/terminals themselves. The yellow and brown wires are the TAC control lines so pay particular attention to those when you're inspecting for damage or broken wires. Keep in mind that the copper wire may be broken inside otherwise intact insulation or under the weatherproofing grommet. Even removing and reseating the connector is often enough to reestablish contact if it's just corrosion on the terminals.

When the engine dies does it stumble and stall out or just shut down like you turned the key off? What about when trying to restart?
 
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darsch

Active Member
Yes u-pull might be cheaper but there doesn't seem to be any of those around here, at least not for that part. I found another one here in BC for $75 + $20 shipping but don't know what the mileage is on it. New remanufactured is $328 unless you know of a cheaper place to buy one?
I had the engine running and wiggled all the wires I could and didn't find any issues. The only thing I spotted was a bare wire on the cam position actuator sensor so I taped that up the best I could.
I disconnected the battery and unplugged the wiring going to the throttle body and the PCM and reconnected it all. The engine runs normal but I haven't gone for a test drive with it. I didn't spray the connectors.
 
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darsch

Active Member
AtlWrk - When the engine dies, it's instant. When it restarts and doesn't run normally, it stumbles like crazy like it's on one cylinder or not getting any gas.
So now it may be a wait and see game the next time I go for a long enough drive to see if it acts up again. I guess I could have it idling and pull the plug for the TAC and see if I get the same results but that still may not tell me the whole problem.
 
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darsch

Active Member
I went on a two hour drive today, mostly highway driving. No issues and no off-idle hesitation. Hopefully I won't have to keep my fingers crossed every time I drive it.
 
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darsch

Active Member
I think I figured it out today after it died again and I couldn't get it to restart and run properly without just staying in limp mode. I unplugged the wire connector going into the throttle body and plugged it back in and it started and ran fine. I'm having a hell of a time getting it to plug back in all the way. It's stopping short of the black clip locking itself into place no matter what I try. I removed the green rubber gasket from the plug and it still won't go all the way in. The male connectors aren't bent, everything looks like it should go together perfectly.
Any ideas?
Should the end of the wire plug casing go right up against the aluminum part of the throttle body or should there be about an eight of an inch gap?
 

MRRSM

Lifetime VIP Supporter
The "Raspberry" colored center pin guide of the Throttle Body Metripac Connector can occasionally pull loose from the connector body where it should be seated flush, just below the outer edge of the plastic connector body. It might need to be removed to check the pin sheaths alignments underneath and then re-inserted. This image shows a good oblique angle to check against the way yours presently appears:

THROTTLEBODYMETRIPAC.jpg
 
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darsch

Active Member
I just took a look at the connector and it is just below the outer edge of the connector body. I tried to force it a little deeper but I don't think it moved. I did manage to just barely get it to click but still might not be all the way. I'll just stop by a shop sometime when I'm driving around again and see what they say. Thanks for the help.
 
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darsch

Active Member
Update:
It died twice today on the way into town and the mechanic said right away it's a common problem with my mileage on the truck plus the drive by wire system and to put another throttle body on it. So Monday I'll pick up the used one and will be trying that one out.
 

Mooseman

Moderator
Actually, it's not a common failure on these trucks although there have been a couple lately. Mine had 300k km and still worked fine. Your symptoms and codes do point to that though.
 
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darsch

Active Member
Is there a computer re-learn procedure that has to be done when another throttle body has been installed? Now when the engine is cold it throws a code every couple of city blocks while driving, sometimes idles at 1500-2000rpm while in limp mode and then when the engine is fully warmed up it runs great.
 
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darsch

Active Member
What I tried this morning was idle for 3 minutes, off for 1 minute, idle for 3 minutes, off for 1 minute, start and go for a spin. Drove for about a mile and it ran perfect as before it would have given me codes by then. Went to drop it off at a mechanic this afternoon and it ran perfect again for 20 miles so hopefully the problem is solved. He's going to do some diagnostics on it while driving and see if it will act up for him but I'm hoping it's fixed now.
 
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darsch

Active Member
They say with all their testing they can't find anything wrong with the throttle body so I may have finally fixed it with that re-learn procedure. Finally some good news.

Now onto the power steering lines and the transfer case motor.
 

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