Fail-Safe Or Limp Mode

PURPOSE
The Electronic Engine Control-V (EEC-V) system has two backup strategies, Failure Mode Effects Management (FMEM) and Hardware Limited Operation Strategy (HLOS). They allow vehicle operation if there is a Powertrain Control Module (PCM) or input failure.

OPERATION
Failure Mode Effects Management
Back-up strategy in the PCM designed to maintain vehicle operation if one or more inputs fail. When a sensor input is perceived to be out of limits by the PCM, the PCM will substitute a fixed sensor value, continuing to monitor the faulty sensor input. If the faulty sensor begins to again operate within limits, the PCM will return to normal engine running strategy.

Hardware Limited Operation Strategy
Special circuitry providing minimal engine operation should the PCM stop functioning properly. Electronic hardware is in control of the system while in HLOS.

HLOS allowable output functions:

- Spark output controlled directly by the PIP signal.

- Fixed fuel pulse width synchronized with the PIP signal.

- Fuel pump relay energized.

- Idle Speed Control (ISC) output signal functional.

HLOS disabled outputs to default state:

- Exhaust Gas Recirculation (EGR) solenoids.

- No torque converter lock-up.