Diagnostic Overview
CAT fault code 102-01 generally indicates intake manifold pressure or boost pressure below the expected range. The ECM is seeing low boost for the current engine speed and load. This can cause low power, smoke, poor acceleration, or derate. A true low-boost condition is usually caused by air leaks, exhaust leaks, intake restriction, turbo control problems, or a worn turbocharger. Sensor problems can also make boost appear low.
Likely Causes
Charge-air cooler leak; loose CAC boot; exhaust leak before turbo; restricted air filter; sticking turbo control; faulty boost sensor; damaged wiring; turbo mechanical wear.
What To Check First
Pressure-test the charge-air system, inspect intake and exhaust piping, compare commanded versus actual boost, and verify the boost sensor reading.