P154B – Intake Air Heater Voltage Signal Circuit (Chevrolet)

By Reinier (Contact Me)
Last Updated 2023-06-26
Automobile Repair Shop Owner

Manufacturer Specific Definitions for P154B

Table of Contents

1. What Does Code P154B Mean?
2. Where is the P154B sensor located?
3. What are the common causes of code P154B?
4. What are the symptoms of code P154B?
5. Get Help with P154B

What Does Code P154B Mean?

OBD II fault code P154B is a manufacturer-specific trouble code that is defined by carmaker Chevrolet as, P154B – “Intake Air Heater Voltage Signal Circuit”, and is set when the PCM (Powertrain Control Module) detects an abnormal or unexpected voltage in the intake air heater’s signal circuit. Note that this is an extremely common code on almost all Duramax, Cummins, and Powerstroke engines.

Since diesel combustion is very inefficient in low to freezing temperatures, almost all large displacement diesel engines are fitted with dedicated heaters in their intake systems to warm intake air. The heated intake air assists in starting the engine as well as reduces the load on the batteries during engine cranking in very low temperatures.

In all cases, the intake air heating element is located in the intake ducting, where it is fed with battery power via the glow plug control module to heat the intake air for as long as the temperature of the engine coolant is below 104 deg F.

In terms of operating principles, some intake air heating systems employ multiple circuits to manage or control the heating element, and in the case of GM and GMC products, this system employs the following circuits-

• IAH temperature signal circuit
• IAH command 1 circuit
• IAH command 2 circuit
• IAH voltage signal circuit
• IAH current signal circuit
• IAH feedback signal circuit

It should be noted that while other manufacturers use similar circuits, code P154B on Chevrolet products refer specifically to a defect or malfunction/abnormality in the voltage signal circuit, which is a circuit that carries information on the voltage that is being fed to the heater element.

Such defects could include wiring issues, or issues with the heater element itself, but regardless of the cause of the problem, when such defects or abnormalities occur, the intake air heater element will not function as expected and the PCM will set code P154B as a result. In addition, the PCM may also illuminate a warning light upon the first failure.

Where is the P154B sensor located?

This image shows the intake air heater element installed in the inlet ducting of a 2004 Duramax engine. In most cases, replacing this part is no more complicated than unscrewing the old part in screwing in a replacement.

However, in other cases, it may be necessary to remove a part of the intake ducting to access the heater element that may be attached to the ducting by four small retaining bolts. When replacing such an element, all gaskets, and seals that were damaged or disturbed during the process must be replaced as well to prevent air and vacuum leaks.

What are the common causes of code P154B?

Some common causes of code P145B could include one or more of the following-

• Defective or damaged intake air heater element
• Poor electrical connections in the heater element’s wiring
• Poor ground connections in the heater element’s wiring
• Damaged, burnt, shorted, disconnected, or corroded wiring and/or electrical connectors in any circuit associated with the operation of the intake air heater element
• Loose or corroded battery terminals
• Discharged or defective batteries
• Blown fuses or fusible links
• Damaged or defective glow plug control module
• Previous repair attempts that involved connecting jumper wires between direct battery power and any command circuit for longer than 20 consecutive seconds

What are the symptoms of code P154B?

Common symptoms of code P145B could include one or more of the following-

• Stored trouble code and possibly an illuminated warning light
• Depending on the nature of the problem, multiple additional codes may be present along with P145B
• It may be impossible to start the engine in sub-zero temperatures
• A hard-starting condition may be present in low to freezing temperatures
• Starter motor failure could occur as a result of extended engine cranking
• Battery failure could occur as the result of extended engine cranking
• The engine may not run at idling speed until it warms up

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