Symptoms

- Engine Light ON (or Service Engine Soon Warning Light) - Engine hesitation

Possible Causes

- Harness or connectors (EGR volume control valve circuit is open or shorted.) - EGR volume control valve stuck open - EGR volume control solenoid valve - Dead (Weak) battery - EGR temperature sensor and circuit - Exhaust

When Detected

High EGR flow control is detected

Description

The ECM monitors the switching frequency ratio of heated oxygen sensors 1 and 2. If too much EGR flow exists due to an EGRC-BPT valve malfunction, off idle engine roughness will increase. If the roughness is large, then the vacuum to the EGR valve is interrupted through the EGRC solenoid valve. If the engine roughness is reduced at that time, the EGRC-BPT valve malfunction is indicated.