Sudden loss of power- fault code P2176

[PaulF]

I have a 2010 Atom 3 245, with about 22.500 km / 14.000 miles on the clock.

A few weeks ago I was letting my engine heat up on idle to do an oil change. After about 10 minutes the revs started jumping up and down very fast, bouncing between 1000 and 2000 rpm. I shut the engine off and started it up again, and it was fine, no issues. Wrote it off in my head and changed the oil. Did an intense hot weather track day the week after, zero issues.

Yesterday I did another track day, this time in the wet (soaking wet). I did some sessions for about 2 hours and suddenly I lose power mid lap. RPMs wouldn't go above 3k rpm, barely could make it uphill. Engine oil temp and pressure were normal, so I limped back into the pits. On idle the car is bouncing between 1000 and 2000 rpm again.

Code reader gives me code P2176:

The P2176 trouble code indicates that the Engine Control Module (ECM) has detected that the throttle body actuator/motor has failed to learn the correct position at which the butterfly valve within the throttle body should be in order to produce a smooth idle for the engine.

What are the causes of the P2176 code?

• A programming error
  A faulty manifold absolute pressure (MAP) sensor
  A large engine vacuum leak
  Large carbon deposits caked on the throttle bore
  A faulty throttle body motor or wiring and connectors associated with it
  A faulty throttle position sensor or wiring and connectors associated with it
  A faulty Engine Control Module

I was on the phone with Steve and we went through the following things:
- visual check of O2 sensor wiring;
- throttle pedal sensor check (looked physically fine and was transmitting the correct position to my AIM datalogger);
- visual check of the wiring to the MAP sensor.

I gave up after those and put the car on the trailer, diagnosis in the rain isn't very fun. I'm meeting with a friend with an Atom to swap some sensors and go over a few things. Definitely will check MAP sensor and spray some brake cleaner on the intake manifold to check for vacuum leaks.

The easy solution would be to go to the factory and have everything checked, but I live in Belgium and COVID restrictions make it very difficult to get to the UK at the moment. Any other ideas or suggestions? Has anyone dealt with this before?

[Atlarge]

I haven't seen this directly but internet wisdom (or lack thereof) suggests it's also worth visually checking the operation of the butterfly valve in the air intake is functioning correctly.

If you have confirmed no vacuum leaks and the TPS is logging the correct position, I'd check to see what the actual valve is doing - maybe also listen to it too ( you can hear the PWM motor wine when the ignition is on and immobiliser disabled), when moving the throttle pedal.

It should move freely and smoothly if not, you may need to clean the intake or there maybe a fault with the drive by wire actuator.

Hope you get it sorted - I too am in a similar situation with something else, getting back to the UK isn't an option at the moment unfortunately!

[PaulF]

Turns out the throttle body motor (operating the butterfly valve) was broken. I bought a second hand throttle body and swapped it in, and the car is running fine again.

[John Scherrer]

Yay !
Glad you got it sorted and thanks for the update.