Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the logical successor to CHARM, I recommend you try it!

Link: lemon-manuals.la

Fuel Trim System Monitor Diagnostic Tests

The fuel trim monitor diagnostic tests monitor the fuel trim values. When the diagnostic tests indicate that the fuel trim system has reached the limits of fuel control at certain engine operating conditions, a fuel trim DTC will set.