Technical Description of OBD-II Trouble Code
The Fuel Fired Heater has been Disabled
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to many OBD-II vehicles (1996-newer), including vehicles from Mercedes-Benz, Land Rover, Opel, Toyota, Volvo, Jaguar, etc. However, the exact repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
If your vehicle has stored a code P2029, it means that the powertrain control module (PCM) has detected a malfunction in the auxiliary or fuel fired heater system, resulting in its deactivation. This code is only applicable to vehicles with fuel fired heater systems.
Creating cabin heat in vehicles with modern, clean-burning diesel engines can be challenging, especially in areas with extremely cold temperatures. Due to the mass of the diesel engine, it may be impossible to heat the engine enough for the thermostat to open, particularly at idle, when temperatures are very low. This can cause a problem in the passenger compartment if warm coolant fails to flow into the heater core. To address this issue, some vehicles use a fuel fired heater system. This system typically consists of a small, pressurized fuel reservoir that supplies an enclosed burner with a regulated amount of fuel when the ambient temperature falls below a certain level. The fuel fired heater injector and igniter may be automatically or manually activated by the vehicle occupants. Coolant flows through the inline burner, where it is heated, and then continues to the passenger compartment. This allows the windshield and other components to be defrosted before the vehicle is driven and before the engine reaches normal operating temperature.
Most vehicles use coolant temperature sensors to determine the heater temperature, although some models also use air temperature sensors. The PCM monitors these temperature sensors to ensure that the fuel fired heater is functioning properly.
If the PCM does not detect an appropriate temperature differential between the coolant entering and exiting the fuel fired heater, it may store a code P2029 and illuminate the malfunction indicator lamp (MIL). The MIL may require multiple ignition cycles with a failure for it to illuminate.
What is the severity of this DTC?
A stored code P2029 will likely result in a lack of heat in the passenger compartment. The stored code indicates that there is either an electrical issue or a serious mechanical failure. In extremely cold weather, it is important to rectify the conditions that led to the storage of this code as quickly as possible.
What are some of the symptoms of the code?
Symptoms of a P2029 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P2029 troubleshooting steps?
To diagnose a code P2029, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information.
You can use your vehicle information source to find a technical service bulletin (TSB) that matches the year, make, and model of your vehicle, as well as the stored codes and exhibited symptoms. If you find a relevant TSB, it may provide helpful diagnostic information.
Use the scanner connected to the vehicle diagnostic connector to retrieve all stored codes and freeze frame data. It is recommended to write down this information before clearing the codes and then test-drive the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode at this time, the code is intermittent and may be more difficult to diagnose. In such cases, the conditions that led to the storage of the code may need to worsen before an accurate diagnosis can be made.
If the code is immediately reset, the next step in your diagnosis will involve searching your vehicle information source for diagnostic flow-charts, connector pin-out charts, connector face views, and component testing procedures/specifications.
If the fuel fired heater has been disabled, the code may need to be cleared immediately prior to testing.
Step 1
Use the DVOM to test the temperature sensors (air or coolant) according to the manufacturer’s specifications. Sensors that do not test within the maximum allowable parameters should be considered defective.
Step 2
Use your vehicle diagnostic information source and the DVOM to test the fuel fired heater injectors and igniters with the system activated. If climate conditions do not permit activation, use the scanner to manually activate the system.
Step 3
If the system switches and other components are functional, use the DVOM to test the input and output signal circuits from the fuse panel, PCM, and ignition switch. Disconnect all controllers before using the DVOM for testing.
