m4a1mustang

Quick question for you guys:

2003 CLK 500 was having trouble starting. When it did start (rare), CEL was on and the car would die while driving after a few minutes. Sometimes it'd restart, sometimes it wouldn't.

Stupidly, I didn't read the code, just assumed it was the CPS. Replaced the sensor and the car started up fine this morning the first two times, however on the third attempt it took a while to start and threw the CEL. Turned the car off, restarted, no CEL. It's been starting fine ever since.

Question is: is this normal after installing a new sensor? Is there an ECU learn period during the first few starts? Since it's starting fine now with no CEL, that's what I'm thinking (read: hoping).

Any advice is greatly appreciated... thanks!

nenad16

well, usually after a crank position sensor has been replaced, it is necessary to reset smooth running adaptations for ECU. this will ensure the new crank sensor's reading pattern is learned and ECU can control the ignition timing more precisely.

m4a1mustang

Understood. And the ECU should start a re-learn phase after the battery has been disconnected for a short period of time, correct? Car seems to be starting/running perfectly now so I'm feeling better about it.

nenad16

you can disconnect the battery, and the ECU will relearn everything, or if you have an access to the SDS or know someone who does, use it reset the adaptations under the smooth running section of the ME system. Also, plugging in the SDS will read the stored fault code(s) that triggered the CEL.

m4a1mustang

Well, its not the CPS. Car didn't want to start again today so its been towed to a local MB mechanic. Hope to figure out what's going on by tomorrow afternoon.

m4a1mustang

Well, local mechanic said it was the CPS but it needs to be calibrated and only a dealership could do it. Dealership saying nothing needs to be calibrated following a new CPS install and it must be something else. Getting towed to the dealership tonight... *sigh*.

nenad16

did he read the ECU fault codes? they must be stored if the CEL was on. If he has the SDS, he can easily reset the adaptations/calibrations and see if that fixes it, if the CPS is the culprit as he stated.

m4a1mustang

He did read the fault codes... it was for the CPS, which I had replaced. He said he didn't have the equipment to go in and reset so we had to tow it to the dealership... though it was starting when we picked it up last night... we just didn't want to risk it dying on the way to the dealer. Waiting to hear back from them today. They seemed to think over the phone that it's something other than the CPS, so they are running their diagnostic tests this morning.

Hopefully whatever it is turns out to be something simple. Would like to keep the car around for a while longer

m4a1mustang

Got the call back from the dealership. Cam position sensor + software updates = $700.