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TPS? Or something more serious?

Driving a 2007 Chevy Aveo, about 80000 miles.

A couple of weeks ago we had a pretty hard storm. My Check Engine light came on, and I had the codes checked:
p0100
p0700
u0073

A little bit after having the codes read, the light went off, and I thought nothing of it.

The other day we had another hard storm, and the light came on again. Codes read again, same codes. Now, though, the light is staying on, and when I start the engine, it revs a couple of times, from 500 RPM to about 1500, then down again, then it settles into place. When the engine is cold, acceleration from a stop is weak, but once it warms up it seems fine. I’m not in any way mechanically inclined, so I have to admit my guess could be far off, but from what I’ve read it sounds like this is related to the throttle position sensor being faulty. But I’m open to advice on other ideas.

FWIW, AutoMD says this is a 100 dollar fix, including labor. Not so sure I buy that, but I can come up with 100 bucks. I just want to know if it could be something more serious.

How did you get TPS out of those codes? Don’t rely on that AutoMD thing to tell you things. Maybe they’re ok for certain things, but in the end an informed human has to be on the other end of any computer thingy.

The P0100 is a MAF circuit malfunction, not TPS. And the P0700 is transmission control system. I cannot tell you much about the u0073 except that it is an issue with signals in the main bus for the whole computer control stuff. So, as I said, TPS?

You’re talking about an issue triggered by heavy rains. The last thing you should think about first is what part to replace. (This is a symptom of having one of those AutoMD-type things). You should first just find out what is getting wet when it shouldn’t be. Are all of your splash shields under the car intact? Inspect the wiring harness for the MAF sensor. (Your actual symptoms could easily be MAF issues). Pull it, clean it, dialectric grease it. Clean the sensor itself. Inspect all of the main connections on your wiring harnesses (the big, fat bundles with big plugs) for looseness/damage. Include the connections at the transmission. But mostly make sure you’re asking about whether or not they are getting wet.

I appreciate the comment.

After you posted, I went down to a different shop and had them pull the codes again, because I figured I had written down the three that I was given incorrectly. Lo and behold, I was right.

U0073 - Module Bus off
U0100 - Lost connection with ECM/PCM
P0700 - Transmission Control Module Request
P0172 - System too rich (this was definitely not on the previous read).

As far as I know, all of the splash shields - in fact I’m sure the whole car is where it’s supposed to be, with the obvious exception of whatever’s coming up here.

Ignore the P0172 for now. I’m still betting dollars to donuts that you have some main harness connectors getting wet.

The communication faults (U0073, U0100) are sometimes caused by low cranking voltage when starting the engine (weak battery). A weak battery may also explain the unstable idle on start up (loss of idle speed control calibration).

“Acceleration is weak from a stop”, P0700 Transmission Control Module request MIL illumination. This indicates a fault is detected and stored in the Transmission control module, is the transmission shifting or is it in limp mode?

Transmission shifts fine. And again, all of the noticable drivability problems occur only when the engine is cold.

Battery shouldn’t be a problem - I replaced the battery about a year ago.

Good to know all it is is something electrical and important getting wet. I’d been worried.

Not to “blow smoke” :wink: but my Aveo has been showing a TPS error since about 80,000 miles. It’s a known issue & we now have to replace it at 110,000 miles a the engine keeps going into “limp home” mode. The dealership wanted us to replace the whole module for about $1,400 but we purchased the sensor for $65. Trouble is, the original is riveted on so drilling & thread tapping will be required, meaning your $100 quote would require a very generous mechanic. It would be nice if sensors were considered part of the power train, since we had a 100,000 mile warranty :frowning: