'99 E300D P0243 code
 

I'm trying to help a benz buddy of mine figure out a problem with a new to him diesel. Keeps getting a CEL and a P0243 code. Clear the code, drives normally until he hits a hard acceleration and it will come back.

done so far:

Checked everywhere for vacuum leaks

swapped the traducers

no joy

Can anybody throw out some ideas on what to check next?

thanks

Check the wastegate to make sure it's operating smoothly and properly. My 98 was doing the exact same thing and swapping the transducers did not resolve or move the problem to the EGR system like would happen if the transducer was the culprit. I ended up swapping the wastegate actuator from my spare parts turbo and lubed up the pivot point and have not had the issue return.

Disconnect the actuator on the turbo and see if the arm moves smoothly. If so it is probably just the actuator which you can test with a mity vac. If the actuator operates fine and holds vacuum then the pivot might be binding up, could happen from soot build up.

Get an _exact_ MB description of the code, this will help diagnosis greatly.

Disconnect the exhaust pipe from the turbo and do a quick run at full throttle to see if it performs ok without bringing code back up.
If it doesn't then suspect the catalytic converter is starting to block up ,hence this only happening at full power wide open throttle.

^good point.

I'm trying to remember the description on the code. I have seen the plugged cat situation on that application and IIRC it happened somewhere after 280k miles. He had made his own fuel for a number of years. Car is now at 350k miles and runs as good as it ever has.

It would possibly tie in with that mileage , its not fully blocked it just cannot handle high gas flow.
You could just hold high revs in a lower gear and see if it puts code up , delete and then repeat

This is why I always push posters to research codes when posting " my car is broken tell me what part to change. " . Posters need to take an active role in diagnosis as this will help them with future problems.

Description will be overboost, code will refer to turbo actuators and a host of other things but the main condition thats causing the code is excessive boost pressure

Trouble codes offer detailed info, glossing over the exact description leads to random changing of parts. Below is what I typed in another thread. The goal of all of this is to give people diagnostic tools that will help in solving future problems.


https://www.peachparts.com/shopforum/tech-help/396616-reving-up-down-code-p-1580-p0100.html

Detailed trouble code descriptions give information as to what the computer is seeing that it does not like. This is critical in forming a diagnostic strategy. Also, some trouble codes are caused by a failure of a part not listed in the trouble code.

Here are 7 generic OBD2 trouble codes related to the coolant temp sensor. Not all codes are used on every car.

Quote:
<table cellspacing="0" cellpadding="6" width="100%" border="0"> <tbody><tr> <td class="alt2" style="border:1px inset"> P0115 Engine Coolant Temperature Sensor Circuit 1 Malfunction

P0116 Engine Coolant Temperature Sensor Circuit 1 Range/Performance Problem

P0117 Engine Coolant Temperature Sensor Circuit 1 Low Input

P0118 Engine Coolant Temperature Sensor Circuit 1 High Input

P0119 Engine Coolant Temperature Sensor Circuit 1 Intermittent

P011A Engine Coolant Temperature Sensor 1/2 Correlation

P011B Engine Coolant Temperature/Intake Air Temperature Correlation

Read more at: https://www.obd-codes.com/p01-codes
Copyright OBD-Codes.com </td> </tr> </tbody></table>


P0116 could be caused by a stuck open thermostat or low coolant.

P0117 could be caused by the sensing wire being pinched to ground

P0118 could be caused by the sensing wire being broken , tied to power or bad plug contact.

P011B could be caused by an intake air sensor problem or someone leaving a trouble light next to the battery to keep it warm ( if the intake air temp sensor / intake duct is near by it will see a temp above engine temp. )

Somewhere in a factory shop manual there will be a detailed code description. This gives clues as what to test to perform. For coolant temp I'd be hanging a volt meter or scope on the coolant temp sensor wire and watching it.

When I had this problem several years ago, it was caused by a hole in my intercooler. My mechanic at the time didn't believe me until we put it on the lift and you could see where a hole was created from something I hit on the freeway.

Thanks everyone for the replies. I’m just advising from a far on this one. Waiting for my buddy to have time to mess with it. From what I’m hearing from him about when it happens I’m putting my bet on waste gate issue.

I resolved a boost issue on a 342,xxx mile '99 model today. Found the boost pressure sensor hose had blown off after becoming plugged. Make sure port into manifold is clear too. I've yet to see a wastegate/turbo fail on one of these cars.