P0542 Code In 6.7 Cummins: What Steps Should You Take?

Engine codes are there to help you find out what’s wrong with your vehicle so you can get it fixed before the situation gets worse. There are a lot of error codes for different parts of your engine, P0542 being one of them.

So, what does the P0542 code 6.7 Cummins engine indicate?

The error code P0542 indicates that the air intake heater “A” circuit has a higher voltage than usual. This means something is wrong with the air intake heater or the relay. If not, it could be a restricted air duct or a damaged blower motor. Rarely, it could be a wiring or an ECM issue.

More details about the air intake heater and the P0542 error code have been discussed in the next sections. 

P0542 Code In 6.7 Cummins: Causes, Symptoms, Solution

The P0542 code is triggered by an issue either on the air intake heater or the heater relay. The other reasons include a restricted air duct, corroded connectors, or a defective blower motor.

In diesel engines, the air intake heater helps the engine to start. So, if that fails, all sorts of starting issues are bound to occur. For example, symptoms like an engine not starting, a longer cranking time, stalling, rough idling, etc.  




Defect in the Air Intake Heater 
  • Engine doesn’t start, 
  • Cranking time longer than normal, 
  • Check engine light illuminated, 
  • Rough idle at cold temperatures, 
  • Stalling Engine.
Clean or replace the heater element
Defect in the Air Intake Heater RelayReplace the heater relay
Temperature sensor not workingReplace the temperature sensor.
The blower motor not workingReplace the motor.
Corroded connectors or damaged wiringClean corrosions and replace damaged wirings.
Restricted Air DuctClean the debris from the air duct.
Faulty ECMReplace the ECM to solve the P0542 Code in 6.7 Cummins 

How to Reset the P0542 Code in 6.7 Cummins

The only way to properly reset an engine error code is to fix it. A lot of components could have gone wrong in this case. So, you will need to check each component to solve the issue. 

Defect in the Air Intake Heater

The code P0542 means the air intake heater circuit has high voltage. So, that means, if the air intake heater circuit may not be working.

The air intake heater is located near the top of the intake manifold. It heats up the air that comes into the intake manifold. This helps with starting the engine and improves engine performance during cold weather.


To make sure the air intake heater is the problem, you have to take it out and examine it. Here are the steps to follow for that:

  • Loosen up the clamp for the boot from the intercooler.
  • Remove the bolt that holds the dipstick tube in place.
  • You can see there are four bolts attaching the heater to the air intake, remove them.
  • Also, there are two bolts that hold the cables; you’ll have to remove those too.

Now, the heater should come right off. The first thing you must look for is if the heater is dirty or clogged. Then, check the bolts and screws to see if they are loose.


If the heater element is dirty, clean it up with a fresh cloth. But if one of the screws is loose, there is no point in tightening it; you will have to replace the element with a new one. Before the replacement, make sure the heater relay works fine.

Defect in the Air Intake Heater Relay

If the air intake heater element is fine, then the next thing you must check is the heater relay.

The air intake heater relay is located near the air intake heater. You will have to run a diagnosis next if the heater element is fine.


To test the relay, you need a multimeter and someone to turn the ignition on. With the multimeter ground cable, touch it to the ground of the solenoid, and then touch the red cable on the solenoid.

With the ignition off and the multimeter set to DC voltage, it should have no readings. But when the ignition is on, there should be voltage on the relay. 


If the relay does not have voltage, you will have to replace it. Here is how-

  • Turn your vehicle off by turning off the ignition.
  • Disconnect the battery, take out the negative terminal first then disconnect the positive terminal.
  • Take out the old relay by unscrewing and disconnecting the wires.
  • Before connecting the new relay, make sure to grease it a little.

Corroded Connectors or Damaged Wiring

You need to check all the wiring that is coming in and out of the air intake system. While you are at it, make sure to check all the connectors to see if they are corroded.


Clean the corrosion on the connectors with the help of baking soda. Make a paste by mixing it with water in a 3:1 ratio. Or, you can use corrosion cleaners. Also, if you find any damaged wiring, have it replaced.

Restricted Air Duct

One of the indirect reasons for triggering code P0542 is the restricted air ducts. So, you will need to check it to see if anything is clogging it. 


Here is how you can test your air duct-

  • Open the hood of the vehicle and locate the engine compartment.
  • Look for housing that is located near the front of the engine, on the driver’s side of the vehicle. This is where the air filter is usually located.
  • Remove the plastic cover to uncover the air filter. 
  • Remove the air filter to access the air ducts. There are two doors in the air ducts, make sure nothing is blocking them. 
  • Also, make sure there is no debris in the air duct.


If the air duct is clogged or filled with debris, make sure you clean it spotless. Also, check if there are two holes in the ducts. Make sure they are not blocked.  

Defective Blower Motor

A defective blower motor can cause high voltage in the air intake circuit of a vehicle when they fail.

Blower motors can fail when they are shorted to ground or if there are problems with the wiring or connections.


So, to confirm that you will need to test it thoroughly.

  • The blower motor is located under the glove box. When you look under it, you will see some plugs with a plastic cover. The blower motor is underneath that. 
  • So, the first thing you will need to do is check if the blower motor gets power. To check that, disconnect the blower motor connector and check continuity.
  • Then you will have to take the blower motor out by unscrewing it. Before testing it out, check if it is damaged or dirty. 
  • You should find a cable with a plug coming out of the motor. That’s the power cable, connect it to a power source, like your car battery. After connecting, it should turn on, otherwise, it’s faulty. 


If the motor is dirty, clean it and reconnect it. If it’s damaged or faulty, it must be replaced with a new one. Before you install the new one, make sure it works too.

Defective Temperature Sensor

The air intake temperature sensor is located on the top left side of the intake manifold. Once you locate it, disconnect the wires. You will find a small knob touching the intake pipe. Lift the knob up a little bit and rotate the sensor counter-clockwise, and the sensor should come off.

Now take a multimeter and set it to measure ohms. Then touch the probes inside the sensor’s plug and measure the resistance.

Then use an air blower to increase the temperature of the sensor, then take a reading of the resistance again. The resistance should be much lower than the previous reading now that the sensor is heated.


If the sensor is not sensitive to heat, then it is defective. Replace it with a new one. When installing, do not pressurize it too much, or you will break it.

Faulty ECM

If everything else checks out, then the ECM is probably at fault. The ECU controls all the other sensors and modules. If that’s the case, you should get quite a few codes, and this needs to be resolved as soon as possible.

ECM testing and diagnosis require a great deal of experience and knowledge on the part of the tester. In such a case, it would be advisable to consult a mechanic. You may have to spend a couple of hundred dollars for a thorough diagnostic. 


An ECM that is faulty can’t be repaired in any way. In other words, if your ECM fails, you’ll need to replace it.

The cost of an OEM ECU may be more than $3000. However, aftermarket ECUs are way cheaper, costing around $500-$800. 

Read More-

  1. How to Fix the P0087 Code In 6.7 Cummins?
  2. P000F Code in 6.7 Cummins: Fast & Proven Solution!


What is an intake air heater?

A heater for the intake of air is an essential component of a cold start system for diesel engines with a high engine capacity. Located next to the intake air collector, they enable the engine to be preheated and started efficiently, ensure its stability, and reduce emissions harmful to human health and the environment.

Is the Cummins 6.7 a V8?

No, the Cummins 6.7 diesel engine is not a V8. It is an inline six-cylinder diesel engine with less horsepower but more torque compared to its competitors. 

Is the 6.7 Cummins a good engine?

Yes, the 6.7 Cummins engine is a good engine. It should be noted, however, that Cummins 6.7L diesel engines are more likely to experience turbocharger problems, EGR system problems, and head gasket problems. Maintaining it properly can extend its life from 250,00 to 350,000 miles.


The P0542 code in the 6.7 Cummins indicates an issue with the air intake pre-heat system. This system is crucial for users who live in comparatively cold areas, as it helps to start and maintain engine performance in cold weather.

If not the air intake heater, the issue could also lie with the ECM, the temperature sensor, the air duct, or the blowing motor. As a result, you must conduct a thorough examination.

But if such things are beyond your skill level, call your mechanic for help.


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