U1900 Mercedes S55 AMG Diagnostic Trouble Code

U1900 Mercedes S55 AMG code definition:
U1900 is a kind of OBD-II Diagnostic U-Network Diagnostic Trouble Code for Mercedes S55 AMG.

U1900 Mercedes S55 AMG is defined as Cylinder 3 Injector Circuit Malfunction. This code means the PCM (powertrain control module, also known as ECM or engine control) has detected a problem in the injector or its wiring, or in injector circuit for cylinder 3. This is because the barometric pressure sensor is part of the MAF sensor. Sometimes, the MAF's sensing wire can accumulate and get covered with dirt, dust and/or oil residue, which can also lead to the error code.

Symptoms

Symptoms of a U1900 Mercedes S55 AMG diagnostic trouble code may include:

Poor acceleration
Cherry red hot catalytic converter
Possible spark knock (detonation / pre-ignition)
The engine oil will exhibit dilution from the ECUs attempts to increase engine temperature. Some vehicles advance the fuel injection timing slightly after top center to afterburn a small amount of fuel to increase exhaust temperatures. Some of this fuel enters the crankcase. When the ECU determines the necessity to regenerate the DPF, the service life of the oil be shortened significantly

Possible Causes :

Defective ECU strategies or components will prevent proper regeneration
The Mass Airflow sensor is a hot wire that senses the volume of air entering the intake manifold. The computer uses this information to control fuel mixture.
A large air leak at or near the number one oxygen sensor would also cause a lean mixture.

Common Misdiagnoses

Crankshaft Position Sensor Circuit Performance Problem
TP Sensor Learn Not Complete Problem
Low Coolant Circuit Problem
Cruise Control System - Vehicle Accel Too High Problem
Kick-Down Switch Failed Short Problem

Repair Processes :

Look for missing ground strap or a rusty ground where the fuel tank is grounded to the frame. Check for damage to the wiring harness connector. Use the DVOM to test resistance and continuity on all system circuits if actuator and sensor resistance levels are in compliance with manufacturer's specifications.

Process Tips

Diagnostic trouble code U1900 Mercedes S55 AMG is not difficult to diagnose and repair. Thus, it always pays to have a qualified technician to look after your vehicle should this error code arise.

Diagnosing this code requires the engine to be in good running shape, without unmetered air entering the engine. If other codes that relates to misfiring condition, lean running or air entering the engine is present, then you must first fix those error codes before U1900 Mercedes S55 AMG.

Fortunately, U1900 Mercedes S55 AMG is a fairly common OBD code, meaning that it applies to all makes and models of vehicles made after 1996.