Straight Pipe Exhaust/Overboost Code?

iakj11 · **Posted:** Mon Jul 29, 2019 4:59 pm

This weekend I installed my new OME suspension and while I was at it I converted to straight pipe exhaust. I took it for a short test drive after completing the work and got a CEL. Here's what appears on the Torque app:

I did a scan a month ago and none of these codes were present.

Is this just an ECM hiccup while it adjusts to different exhaust pressure? I did have to move some of the turbo control components out of the way to install the front right strut assembly, but did not disconnect anything.

After seeing the CEL, I physically checked the connections of all of the little hoses and wires, and all seem correct.
My next move is going to be clear the codes and see if they come back. Anything else I should do or check first?

TKB4 · **Posted:** Mon Jul 29, 2019 5:27 pm

If it ran OK thats all I would do for now except you may want to make sure airbox sensors are in good if you altered it and make sure the turbo actuator arm is freely moveable.

mass-hole · **Posted:** Mon Jul 29, 2019 6:42 pm

I don’t think you freed up all that much pressure to cause an overboost. I put a new, upgraded turbo with larger compressor and turbine on my liberty and havent had issues with it over or underboosting.

It has to overboost for a certain period before you get that code so it sound like maybe something is not working quite right.

iakj11 · **Posted:** Mon Jul 29, 2019 9:36 pm

TKB4 wrote:

If it ran OK thats all I would do for now except you may want to make sure airbox sensors are in good if you altered it and make sure the turbo actuator arm is freely moveable.

I made sure the MAF and Mercedes sensors were plugged in well and the wires looked ok. Any advice on how to check the actuator arm? If I'm understanding right I just need to manually verify that it moves with the engine not running, but how do I get to it?

WWDiesel · **Posted:** Mon Jul 29, 2019 10:15 pm

First thing I would do is replace the MAP sensor. It is the only sensor that can produce an over-boost DTC.
Freeing up the exhaust will produce lower backpressure on the turbo which will contribute to faster turbo response time and lower EGT's.
But if you are getting an overboost DTC, it means the MAP sensor is seeing an above it's upper range of pressure.
Range: 3 bar (20 kPa @ 0.4V / 300 kPa @ 4.65V)

iakj11 · **Posted:** Tue Jul 30, 2019 7:06 pm

New MAP sensor is on the way!

iakj11 · **Posted:** Sun Aug 04, 2019 9:28 am

I cleared the codes and drove it a few times and the cel did not reappear. I watched the boost with the torque app each time I drove and did notice at least one erratic spike, as in a boost reading of over 20 for just a split second with light throttle just after idle. I've gone ahead and put in the new MAP sensor, and after a couple more drives, all seems well again. Thanks for the help!

WWDiesel · **Posted:** Sun Aug 04, 2019 3:03 pm

iakj11 wrote:

I cleared the codes and drove it a few times and the cel did not reappear. I watched the boost with the torque app each time I drove and did notice at least one erratic spike, as in a boost reading of over 20 for just a split second with light throttle just after idle. I've gone ahead and put in the new MAP sensor, and after a couple more drives, all seems well again. Thanks for the help!

Straight Pipe Exhaust/Overboost Code?

Who is online