P028B: Charge Air Cooler Cooling Fan Performance/Stuck Off

What does P028B mean?

Some vehicles – mainly commercial and off-road machines, or cars with a separate cooler for a coolant-cooled charge air cooler – have their own fan for the charge air cooler, switched by the engine module; a Deere patent describes such a fan that is also reversed to blow out dirt. P028B means the module commands the fan on but sees no effect – no speed or current feedback from a fan control module, or the charge air does not cool – although the circuit is electrically sound (circuit faults are P028A, P028D and P028E). The charge air then gets hotter, which can limit boost and power. No manufacturer document using this code was found; the description rests on CARB's output component requirement.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Warning light (manufacturer-dependent)
• Loss of power in heat or at low speed
• High charge air temperature, possibly P026A

Common causes

• High Fan motor seized or worn
• Medium Fan blocked (debris, dirt, ice)
• Medium Fan relay or fan control module without output
• Low Fan fuse or supply

Likelihood is a general estimate across vehicles; your make and model may differ.