What Does It Mean?
This generic powertrain diagnostic trouble code (DTC) generally applies to many OBD-II vehicles. This may include, but is not limited to, vehicles from Jeep, Jaguar, Dodge, BMW, Land Rover, Toyota, VW, Ford, Mitsubishi, Mazda, etc.
A stored P050C code means that the Powertrain Control Module (PCM) has detected a problem with the engine coolant temperature performance. Cold start is a term used to describe an engine driving strategy that is implemented only when the engine is at (or below) ambient temperature.
The engine coolant temperature is monitored by the PCM using one or more Engine Coolant Temperature (ECT) sensors. The ECT sensor consists of a brass (or plastic) housing with a thermistor inside. The housing is designed to be screwed into the engine block, cylinder head, or intake manifold; where the engine’s cooling passages are located. When the thermostat opens, the coolant flows past the tip of the ECT sensor (where the thermistor is located). The ECT sensor receives a reference voltage and a ground, but the sensor completes the circuit. When the engine coolant temperature increases, the resistance of the thermistor decreases. The result of this decrease in circuit resistance is a higher voltage input to the PCM. When the engine coolant temperature decreases, a reverse action occurs and the circuit voltage decreases. The PCM receives these variations in circuit voltage as changes in engine coolant temperature.
Some vehicle applications use multiple ECT sensors. A common location for a secondary ECT sensor is in one of the radiator tanks. The PCM compares the input signals between the ECT sensors to determine if the engine coolant is flowing effectively.
In most cases, the engine coolant temperature is also compared to the ambient temperature under cold start conditions. The ambient temperature sensor operates similarly to the ECT sensor and is normally located near the grille.
If the PCM detects a difference between the ECT sensors and/or the ambient temperature sensor that exceeds the maximum threshold, under cold start conditions, a P050C code will be stored and a Malfunction Indicator Lamp (MIL) may be illuminated. Several ignition cycles (with a failure) may be required for the MIL to illuminate.
Cold Car:
How Severe Is This DTC?
A lack of engine coolant efficiency can lead to poor drivability under cold start conditions, decreased fuel efficiency, and poor heating performance. A P050C code should be considered serious and rectified as soon as possible.
What Are Some of the Symptoms of the Code?
Symptoms of a P050C engine code can include:
Rich exhaust
Cold driveability issues
No heat inside the passenger compartment
Codes associated with the ECT sensor
What Are Some of the Common Causes of the Code?
Causes
of this code can include:
Faulty primary or secondary ECT sensor
Faulty ambient temperature sensor
Shorted or open circuits or connectors
Bad thermostat
Low coolant level
What Are the P050C Troubleshooting Steps?
Diagnose and repair codes associated with the ECT before attempting to diagnose P050C.
Start by ensuring the engine is full of coolant and not overheating. If it is full of coolant and not overheating, a visual inspection of the wiring and connectors of the ECT sensor system would be my next concern.
When diagnosing a P050C code, I would have access to a reliable vehicle information source, an infrared thermometer with a laser pointer, a diagnostic scanner, and a digital volt/ohmmeter (DVOM).
You will need diagnostic flowcharts, wiring diagrams, connector pinout views, connector pinout diagrams, and component testing procedures and specifications to accurately diagnose a P050C code. This information can be found in your vehicle information source.
Connect the scanner to the vehicle’s diagnostic port. Retrieve all stored codes and freeze frame data and note them in a safe place. This can be helpful for further diagnostic process. Clear the codes and test drive the vehicle to see if the code resets.
If the P050C is immediately reset, turn the key on with the engine off (KOEO) and reconnect the scanner. Use the infrared thermometer to check the actual coolant temperature at the appropriate location near the ECT sensors. Observe the ECT data on the scanner and see if including only the relevant items for a faster and more accurate data response. If the ECT displayed on the scanner does not match the actual coolant temperature, follow the diagnostic steps below.
If a crazy ECT is displayed on the scanner data display (like -38 degrees):
With KOEO, test the ECT reference voltage and ground
Disconnect the ECT sensor connector
Probe the reference circuit using the DVOM’s positive test lead
The negative test lead should be used to probe the ground circuit of the same connector
The DVOM display should reflect the reference voltage (usually 5 volts)
You can use the DVOM to test individual coolant and ambient air sensors using the manufacturer’s specifications and testing procedures. Sensors that do not match the specifications should be considered faulty.
Search for applicable Technical Service Bulletins (TSBs). The information found in the correct TSB will help you a lot in your diagnosis