Fault code P2604 – intake air heater “A” circuit range/performance

Fault code P2604 is called “Intake Air Heater “A” Circuit Range/Performance” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P2604

OBD-II trouble code P2604 is defined as “inlet air heater circuit “A” operating range mismatch”. It is set when the PCM ( powertrain control module) detects an abnormal input voltage in the intake air heater circuit.

Fault code P2604 – intake air heater

Typical intake air heating systems consist of a heating element, a blower to move the heated air into the engine. As well as various electrical components including wiring, connectors, temperature sensor and relays.

The function of the intake air heater is to heat the intake air to improve combustion at low temperatures.

Note that the intake air preheater only kicks in when the ambient temperature drops below the level specified by the manufacturer. Intake air preheating has a number of advantages, among which is a reduction in fuel consumption. Because the hot air-fuel mixture burns more completely than the cold mixture.

Voltage variations in the input circuit that are out of the specified range will cause fault code P2604 to appear. This is followed by a control lamp, which signals the occurrence of the error.

It is not always the case that the first fault sets the code and activates the warning lamp. In some cases, several failure cycles are required before the indicator lamp will turn on.

Symptoms of vehicle malfunctions

The main signal that an error P2604 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will illuminate (the code will be stored as a fault).
  2. There may be no symptoms other than the stored fault code.
  3. Longer than normal engine starting time.
  4. Uneven idling at low temperatures.
  5. Engine may stall at idle at very low temperatures.
  6. Increased fuel consumption.

Fault P2604 is usually a moderate error, but can sometimes be serious depending on the specific symptoms of the malfunction. Therefore, when a problem is detected, it is recommended that the error be corrected as soon as possible.

Factors that can cause this error code

The error code P2604 can mean that one or more of the following problems have occurred:

  • Faulty heater element relay.
  • Heater element itself is defective.
  • Corroded or damaged connector.
  • Faulty or damaged wiring.
  • Damaged or clogged air duct.
  • Defective fan motor.
  • Faulty temperature sensor.
  • Sometimes faulty PCM module is the cause.

How to fix or reset OBD-2 code P2604

Some suggested steps for troubleshooting and fix the error code P2604:

  1. Check and replace heater element relay if necessary.
  2. Heating element is defective Replace if defective.
  3. Clean corrosion from connectors.
  4. Repair or replace wiring.
  5. Replacing damaged air ducts and air ducts.
  6. Replacement of fan motor.
  7. Check and replace temperature sensor if necessary.
  8. If error persists, check PCM module.

Diagnose and repair of problems

The first step in the P2604 troubleshooting process, is to review the Technical Service Bulletins (TSB). In some cases, this can save you a lot of time in the long run by pointing you in the right direction.

The heater may not activate automatically if the ambient or engine temperature is above the limit set by the manufacturer. The circuit should activate when the “ON” command is given with the scanner or when power is applied manually.

Advanced steps

The advanced steps to diagnose fault P2604 are very specific and require the proper advanced equipment to perform accurately. These procedures require a digital multimeter and specific vehicle technical manuals.

Voltage requirements depend on the specific year of manufacture, model and engine type of the vehicle.

If voltage is applied to a component that is not functioning, that component is probably faulty and needs to be replaced. If power is not available to operate the circuit, a continuity check may be required to identify faulty wiring or components.

On which vehicles does this problem occur most frequently

Fault code P2604 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Chevrolet
  • Dodge
  • Ford
  • GMC
  • Honda
  • Nissan
  • Volvo

Fault code P2604 can sometimes be found with other errors. The most common are the following: P0540, P0541, P0542, P0543.

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