Everyone knows that when the check engine light comes on, you have an issue. But when it flashes, does that mean it’s a bigger problem? We may never know. Follow this Real Fix to see how a code 6805 on a 2004 Volvo S60 was diagnosed and repaired.
Vehicle
2004 Volvo S60 R 2.5L
Title
Code 6805, Engine Idles Rough, Replaced Ignition Coil, Turbocharger Boost Control Solenoid
Complaint
The customer states the engine idles rough. The customer also states the check engine light was flashing.
Cause
Confirmed the customer’s complaint and found the engine idled rough. Connected a scan tool and found code 6805 – Turbocharger (TC) control valve, boost pressure fault. Pressure too high. Performed a visual inspection of the turbocharger boost control solenoid electrical connector and vacuum hoses and found no apparent faults. With the scan tool connected, started the engine, activated the turbocharger boost control solenoid and found no audible click when the solenoid was activated. With the engine at idle disconnected the output vacuum hose from the turbocharger boost control solenoid valve to the turbocharger boost control valve. connected a vacuum gauge and found vacuum was present at the turbocharger boost control solenoid vacuum outlet with the turbocharger boost control solenoid deactivated indicating an internal fault with the turbocharger boost control solenoid valve. Performed a road test after replacement of the turbocharger boost control solenoid and found the check engine light began flashing. Connected the scan tool and accessed freeze frame data and found the misfire counts for cylinder 4 were excessive. Used the lab scope with the appropriate adapter on the ignition coil #4, started the engine and found the specified 40 kV firing line on the lab scope was erratic and had dropouts indicating an internal fault in ignition coil #4. These test results verified the turbocharger boost control solenoid and the ignition coil #4 were faulty.
Correction
Replaced the ignition coil and turbocharger boost control solenoid, cleared codes, performed a road test and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned.
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