Chrysler
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    Fuel System Rich Conditions
Cause:
    Engine running in closed loop, altitude less than 8000 ft., BTS input over 20°F, then test started and PCM detected that a rich air/fuel condition was present in the test period.

Ford
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    Fuel System Too Rich Conditions
Cause:
    Engine running at Cruise speed for 3-4 minutes, then the PCM detected that the Adaptive Fuel Control System was at its lean correction limit (due to a rich A/F ratio)

Generic
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    System Too Rich

GM
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    Fuel Trim System Rich Conditions
Cause:
    No PCM codes set, ECT input at 176-230°F, engine speed 1000-4000 rpm, throttle angle steady and less than 91%, VSS under 70 mph, Purge duty cycle below 80% and PCM detected LONGFT was over 100, or SHRTFT below 94, condition met for 25 seconds

Nissan
Type:
    Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description:
    Fuel trim - Bank 2 - mixture too rich
Cause:
    Wiring, exhaust system, HO2S front, fuel system, injector, MAF sensor, ECM