Vehicle: 2002 Mercedes Benz C 230 Kompressor (203.747), L4-2.3L SC (111.981), Automatic Transmission/Transaxle

Mileage: 178,429

Problem: The owner of this C-class Mercedes reported that the engine would start and run for about five minutes, then it would die and not restart for a while. It made no difference if the engine was cold or warm. The malfunction indicator light (MIL) was on.

Case Details: The technician took the vehicle on a test drive with a scan tool connected to verify the customer’s concern. While on the test drive, he found the following diagnostic trouble codes (DTCs).

• P2004 - Altitude Pressure Sensor (B18) Signal Short/Open
• P2035 - ME-SFI (N3/10) Control Module Fault
• P2041 - ME-SFI (N3/10) Control Module Internal Fault

He also noticed that when the engine stalled, communication was lost with the ECM (a.k.a. ME-SFI Control Module). NOTE: Another shop had already tried replacing the ECM, but that did not fix the problem. It was time to call ALLDATA Tech-Assist for some friendly advice.

The Tech-Assist consultant said that any faulty sensor connected to the ECM could cause the stalling and ECM failed communication issues. An operating time of about five minutes may be all that's needed for a faulty sensor to fail internally and bring the entire system down. Then, once the sensor cools off and begins functioning normally, the cycle starts all over again. He recommended focusing on DTC P2004 first.

The technician inspected the altitude pressure sensor (B18) as recommended and found it was faulty.

Confirmed Repair: He replaced the altitude pressure sensor (B18), cleared the DTCs and road tested several times to verify that there were no more stalling issues. Mystery solved!