Technical Description of OBD-II Trouble Code
The code P0253 refers to Injection Pump Fuel Metering Control A Low (Cam/Rotor/Injector). This code is commonly found in diesel fueled OBD-II equipped engines, including Mercedes Benz and VW vehicles. The specific repair steps may vary depending on the vehicle’s year, make, model, and powertrain configuration.
The Injection Pump Metering Control Circuit “A” is typically located inside or on the side of the injection pump, which is bolted to the engine. This circuit consists of a Fuel Rack Position (FRP) Sensor and a Fuel Quantity Actuator.
The FRP sensor converts the amount of diesel fuel delivered by the Fuel Quantity Actuator into an electrical signal for the Powertrain Control Module (PCM). The PCM uses this signal to determine the appropriate amount of fuel to inject into the engine based on its operating conditions. If the input from the FRP sensor does not match the expected values stored in the PCM’s memory, the P0253 code is triggered. The PCM also checks the voltage signal from the FRP sensor during initial Key On.
The P0253 code is set when the voltage at the FRP sensor stays below a certain level for an extended period of time. This code is typically associated with an electrical circuit issue. To identify the specific “A” part of the circuit for your vehicle, refer to a vehicle-specific repair manual.
Troubleshooting steps may vary depending on the manufacturer, type of FRP sensor, and wire colors.
Severity of this DTC
In this case, the severity of the P0253 code is considered to be not severe. Since it is an electrical failure, the PCM can compensate adequately for it.
Symptoms of the Code
Some symptoms of a P0253 trouble code may include:
Common Causes of the Code
Some common causes for the P0253 code may include:
Troubleshooting Steps for P0253
A good starting point is to check for technical service bulletins (TSB) specific to your vehicle. There may be a known issue with a known fix provided by the manufacturer, which can save time and money during diagnosis.
Next, locate the FRP sensor on your vehicle, which is usually mounted inside or on the side of the injection pump bolted to the engine. Inspect the connector and wiring for any signs of damage such as scraping, rubbing, bare wires, burn spots, or melted plastic. Disassemble the connector and inspect the terminals for signs of burning or corrosion. Clean the terminals if necessary using electrical contact cleaner and a plastic bristle brush. Apply electrical grease to ensure proper contact.
If you have a scan tool, clear the diagnostic trouble codes from memory and check if the P0253 code returns. If it does not, the issue was likely related to the connections.
If the P0253 code does return, further testing of the FRP sensor and its associated circuits is necessary. With the Key Off, disconnect the electrical connector at the FRP sensor. Use a Digital Voltmeter to measure the voltage between the black lead (ground) and the red lead (power) at the FRP sensor wiring harness connector. The voltmeter should read either 12 volts or 5 volts according to the manufacturer’s specifications. If not, repair the power or ground wire, or replace the PCM.
If the previous test passed, the signal wire needs to be tested. With the connector still disconnected, move the red lead of the voltmeter from the power wire terminal to the signal wire terminal. The voltmeter should now read 5 volts. If not, repair the signal wire, or replace the PCM.
If all previous tests have passed and the P0253 code persists, it is likely that the FRP sensor or Fuel Quantity Actuator has failed. However, a failed PCM cannot be ruled out until the FRP sensor or Fuel Quantity Actuator is replaced. If unsure, seek assistance from a trained automotive diagnostician. Note that PCMs must be programmed or calibrated to the vehicle for correct installation.
