P040A Exhaust Gas Recirculation Temperature Sensor Circuit
OBD2 Error Codes

P040A Exhaust Gas Recirculation Temperature Sensor Circuit

P040A Exhaust Gas Recirculation Temperature Sensor Circuit

OBD-II DTC Datasheet

Exhaust Gas Recirculation Temperature Sensor Circuit

What does this mean?

This is a generic Diagnostic Trouble Code (DTC) and is commonly applied to OBD-II vehicles. This may include but is not limited to Mazda, VW, Audi, Mercedes Benz, Ford, Dodge, Ram, etc.

Although general, the exact repair steps may vary depending on the model year, make, model, and transmission configuration.

Before the efficient introduction of exhaust gas recirculation systems in vehicles in the 1970s, engines actively consumed unburned fuel and released it into the atmosphere. These days, on the other hand, a car must have a certain emission level in order to continue production.

The use of exhaust gas recirculation systems has resulted in significant emissions reductions by recirculating fresh exhaust gases from the exhaust manifold and / or other parts of the exhaust system and recirculating or re-burning them to make sure we burn effectively the fuel we pay for. by their stubborn efforts. earned money!

The function of the EGR temperature sensor is to provide a means for the ECM (engine control module) to monitor the EGR temperature and / or adjust flow accordingly with the EGR valve. This is easily done with a conventional resistor type temperature sensor.

Your OBD (On-Board Diagnostic) scan tool may show P040A and related codes active when the ECM detects a malfunction in the EGR temperature sensor or its circuits. As I mentioned earlier, the system includes hot exhaust, not only that, but you are dealing with one of the hottest areas in the car, so be careful where your hands / fingers are, even with the engine off for a short period of time. time.

Code P040A The EGR temperature sensor circuit is set by the ECM when a common fault is detected in the EGR "A" temperature sensor circuit. Consult your specific vehicle repair manual to determine which part of the chain is "A" for your specific application.

What is the severity of this DTC?

The severity here greatly depends on your particular problem, but I would not classify it as serious given the fact that the entire system has been introduced into vehicles simply as an emission reduction strategy. That being said, exhaust leaks are not “good” for your vehicle, nor are leaking or faulty EGR temperature sensors, so maintenance is key here sooner rather than later!

Example of an exhaust gas recirculation temperature sensor: P040A Exhaust Gas Recirculation Temperature Sensor Circuit

What are some of the symptoms of the code?

Symptoms of a P040A trouble code may include:

  • Failed state / province smog or emissions test
  • Engine noise (knocking, rattling, ringing, etc.)
  • Louder exhaust
  • Excessive exhaust odor

What are some of the common causes for the code?

Reasons for this P040A engine code may include:

  • Defective or damaged EGR temperature sensor.
  • Exhaust gas recirculation temperature sensor gasket leaking
  • Cracked or leaking exhaust pipe where the sensor is installed
  • Burnt wire harness and / or sensor
  • Damaged wire (s) (open circuit, short to power, short to ground, etc.)
  • Damaged connector
  • ECM (Engine Control Module) problem
  • Bad connections

What are some steps to troubleshoot the P040A?

Basic step # 1

The first thing I would like to do here is to check everything we can see by simply visually inspecting the sensor and the surrounding EGR system, specifically looking for exhaust leaks. Also check the sensor and its harness while you are there. Remember what I said about those high temperatures? They can damage the plastic and rubber wires, so check them carefully.

TIP: Black soot can indicate an indoor exhaust leak.

Basic step # 2

Many EGR problems that I have seen in the past have been caused by the accumulation of soot in the exhaust, which can be caused by a number of reasons (poor maintenance, poor fuel quality, etc.). This is no exception in this case, so it may be helpful to clean the EGR system, or at least the temperature sensor. Be aware that sensors installed in exhaust systems can feel pinched when trying to unfasten.

Remember that these sensors are subject to significant temperature fluctuations, so a little heat using an OAC torch (not for the layman) can help weaken the sensor. After removing the sensor, use a carburetor cleaner or similar product to effectively saturate the soot. Use a wire brush to remove excess soot from accumulated areas. When reinstalling a clean sensor, be sure to apply anti-seize compound to the threads to prevent galling.

NOTE. The last thing you want to do here is to break the sensor inside the manifold/exhaust manifold. This can be a costly mistake, so take your time when breaking the sensor.

Basic step # 3

Verify the integrity of the sensor by measuring the actual electrical values ​​versus the manufacturer's desired values. Do this with a multimeter and follow the manufacturer's contact verification procedures.

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