'Reduced Engine Performance' on an Ecotec 2.2

[pbm]

While driving home from work last night on The Cross Bronx Expressway (aka: the longest parking lot in America or Highway 95) my Saturn Ion went into limp mode with the 'Reduced Engine Performance' light illuminating. I made it off the highway (into the ghetto) and parked. I was fortunate to get a ride home (50 miles) with a guy that I knew was heading my way. I went back this morning and she started right up but showed Code P2135 and P2176. I made it home without a problem and thought it might be an aberration until it happened again this afternoon.
When I read the new codes it showed P2101 and P1516...I cleared them and she ran good the rest of the day.
From what I gather this 'limp mode' happens because the 'drive by wire' goes into 'safe mode' so that the engine doesn't 'run away'...
In other words an electrical anomoly causes the engine to 'limp' inorder to avoid unintended acceleration. It looks like I have either an electrical problem, a ECU problem or a TPS problem.
Is anybody familiar with this problem on a 2.2 Ecotec and if so..what do I do? Thanks

 

[mechanicx]

The PCM is a a good possibility. Is it an '05-'06? Some of them had issues with their PCM.

 

[hardcore302]

ahh the cross bronx//

7 mpg observed lol

 

[daves87rs]

Gotta be the PCM...don't hear that very often. Though early Ions did have some odd issues....


From someone who has three 2.2 Ecotecs, it's never happened here...

 

[mattd]

Throttle body. There are MANY issues with GM throttle bodies that throw the P2135 throttle sensor 1, 2 correlation code. I have done several. Order just the electronics part if possible, if not the whole T/body. IIRC there is a TSB also.

Edit: No TSB but every single one of those codes are related to throttle unit. Check harness at throttle unit also some corrode and pins become loose causing high resistance.

 

[pbm]

Thanks guys....I couldn't get to the computer yesterday to check for your answers.
I pretty much have it narrowed down to PCM or TB....I hate to take it to the stealer for $$ reasons.
Is this something that a regular mechanic would be able too diagnose or do I need the dealers equipment?

 

[SwampSurvivor]

Well, the dealer is most likely going to end up throwing a TB at it. If TBs are a problem on this car, and it's throwing the same codes - that's what they are going to throw at it first.

If you've narrowed it down to two issues ... replace the cheapest one first. See if you can get the electric throttle body from a junkyard or something to see if that helps the problem.

 

[jim302]

Definitely start with the throttle body. Then, check for electrical issues before assuming that the PCM is bad. The PCM is always a possibility for just about any code, but is never the first thing that should be replaced just by guessing. Sensor and electrical issues can cause some strange behavior and odd codes.

P2135 = P2135 Throttle Position Sensor 1-2 Correlation Error
P2175 = a reduced power / limp mode code, caused by P2135 in this case

P2101 = Throttle Actuator Position Performance
P1516 = Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance

Basically, there PCM sees two TPS signals, and they should both think the position is the same (the signal may be different, but it should correlate to the same position). This will put the car into limp mode and set a code.

The other two codes are indicating that the throttle position (as reported by the TPS) is not what it expects.

 

[pbm]

I found a TSB 070604003 which states that PCMs with specific build dates would be replaced under warranty for 8 years or 80K because they throw some of these codes P2135, P2138, P1516.
I'll take the car into a dealer next week to see if I have one of the faulty PCM's and if I'm covered.