I was driving on Friday night and suddenly got a check engine light and a message Engine Power Reduced. I pulled over and stopped and turned off the ignition.

After about 5 minutes the car started back up with an illuminated CEL, and seemed to drive normally. I checked online and came across this forum.

I went to AutoZone today and had them do an OBDII code check and they turned up 2 error codes:

P2135: Throttle position sensor (TPS) 1-2 correlation.

Explanation: The ECM has detected that TPS1 and TPS2 disagree more than 4.5 percent for less than 1 second.

Probable causes:

1. Poor electrical connection
2. Failed TPS


P2119: Throttle actuator control (TAC) system fault.

Explanation: The ECM detected that the throttle blade did not return to the correct at rest position.

Probable causes:

1. Check for throttle plate obstruction.
2. Binding throttle plate-Throttle body failure
3. Throttle plate actuator failure.


OK, so AutoZone cleared the CEL and I have not had the problem on the way home but I will keep an eye on it. I figure that the first error code could cause the 2nd one to be read because if the Throttle Position Sensor is worn slightly it could have had a contact drop out causing the reading at the ECM for the Throttle Position Sensor and the Throttle Actuator Control not to read the same at the ECM for a few milliseconds.

Before the error code was checked, while the CEL was still on, I went on the road at about 55 mph and set the cruise control, and the cruise control worked, surprisingly.

It had been my understanding from the reading I did on the "Engine Power Reduced" problem, that the cruise control would not work if there was a continuous error condition being read. (I could have misread this)

The other thing that was on my mind about this problem was that I have never replaced my oxygen sensors in the car, and I have high mileage.(2007 HHR Lt, approximately 170,000 miles) This is the first time the CEL has come on in this car, believe it or not! This car has been nothing but ultra reliable under a lot of driving across country (It is not unusual for me to take trips >1100 miles at a time, and in extremely cold environments (upstate NY, and Northeastern US during the dead of winter.)

My guesses, could be the wiring harness, It could be that my TPS is worn, (I think this is more likely) My Throttle assembly might need to be cleaned or I might have some other electrical issue that falls under the category of something I don't know that I don't know.

I do know that the O2 sensor might be having issues because my gas mileage is not quite as good lately as it has been, (I usually get about 32mpg, lately it has been closer to about 26.) and at my last oil change the subject of the O2 sensor being due to be replaced was mentioned so it (I thought there were 4 of them so they) might just be reading lean, causing both a drop in gas mileage and engine performance. The car definitely doesn't seem to accelerate when getting on the on ramp of the highway as vigorously as normal.

I felt I wouldn't be doing my due diligence if I didn't also come on and mention it here because perhaps someone with the same symptoms could shed some light, or someone else could be helped. (I can hope.)

Thanks in advance, This forum has a lot of insightful and fun posts!

 

Welcome to the site

Here is a thread that may help. https://www.chevyhhr.net/forums/problems-service-repairs-42/p2135-code-help-48870/

 

Start by inspecting the Throttle Body, it probably is dirty.
There are a few different types of OBDII codes.
There are 2 O2 Sensors.
We have recently been discussing reduced MPG in the very cold weather. I got 31 MPG when the ambient was 50ish F, and 25 MPG when the ambient was in the single digits F.

Personally, I would wait for the OBDII to tell me to replace an O2 sensor. They are not cheap, and not really a "maintenance" part except for shops that want to also flush your power steering fluid (they use a 3rd party check off sheet in the hopes of scaring people).

 

I would tend to agree with that assessment on the Throttle Body Don. I was getting off the highway tonight and hit some bumps, and got the "reduced engine power" error again.

I stopped like before and the first several tries the car would not start, I even saw a message that said "Engine Disabled". After a few tries I got it started and drove across some shallow bumps in the parking lot, which was enough to cause the "Reduced Engine Power" error to come back twice.

I stopped , opened the hood and messed with the connectors, nothing felt loose or dislodged based on any of the diagrams I looked at. Just for good measure I opened and closed the fusebox under the hood and it was kinda stuck open, it took a bit of percussive maintenance to get it closed, but.. good news, the car started right up and made the 8 mile trip back to my garage without so much as a hiccup, in fact the accelerator did seem more responsive than before but I wasn't pushing it, just glided home avoiding potholes. Cruise control worked too.

I agree about the O2 sensor, and it has been in the 20s-30s where I am, but I have been in -30 with that vehicle before and it probably did have a reduction in mileage but things like that are hard to notice when driving through mountainous territory and it is snowing sideways! (Upstate NY around Lake Placid and Franklin County, a stones throw from the Canadian border, is not to be taken lightly!) You are probably right about the temp and we are talking about a 4mpg difference, but it is not a fluke. It is a "Something".

The mechanic wants to do a transmission flush along with the O2 sensor so Im going one repair at a time just so I don't break the bank and so we have some idea of what fixed what. Things like this are like adjusting BIOS settings on a pentium 1, you make one change at a time, otherwise the "Differential Diagnosis" goes sideways. What happened tonight was a good thing, lucky even. It is clear the error is under the hood.

I am not worried about the 02 sensor at all at this point. I have driven a 1982 VW rabbit from Albany NY to St Louis MO, non-stop with a O2 sensor on it that was clearly .. broken.. and made it.. but 2 hours after arriving, both back tires went flat! .. that was luck! Sometimes it is important to note the difference! Making it home tonight was luck too.

Thanks for your help! Both of you!

 

Based on your second paragraph of your last post, I would guess a faulty fuse box. That is a relatively common issue.

The box is composed of 2 pieces, upper and lower obviously. And has a tendency to cause problems as you described.

It's kind of a male, female fit.....pins into the connectors to the fuse portion of the box.

 

none of the fuses seemed to be blown or loose, no debris or anything. This was my rationale for opening it to check. Both Headlights, all the lights , AC, Heater, Fans, interior lights, LED map light, wipers, Stereo and rearview mirror positioning motors all work,, the only thing that is out is the light in the shifter assembly and It has been out for most of the life of the vehicle.. just never got around to fixing it. (I do suspect that if the fusebox was faulty I would be having bigger problems.)

I just suspect the throttle body / connector was luckily just one of those things that responded to an "Arthur Fonzerelli style Slap".

 

NOT the fuses, the top HALF of the fuse BOX. The 2 halves tend to loosen up.

There are blades under each fuse on the BOX that mate to the bottom of the BOX.

Ignore if you want, but it happens more than you'd think.

 

Thanks donbrew. I guess I did not explain well enough.