DTC P0340: Camshaft Position Sensor Circuit: Description

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

Electronic Ignition (EI) module supplies 5 volts to cam signal circuit whenever it determines cylinder No. 1 or cylinder No. 3 has just fired on its compression stroke. EI module uses capacitive pick-up plates located under 1/4 and 2/3 coil packs to determine polarity sequence and voltage amplitude of cylinder 1/4 and 2/3 secondary ignition. ECM has an internal resistor tied to ground on signal line in order to detect zero volts when no cam signal is received. Since engine firing order is 3-4-2-1, ECM expects to see a bit pattern of 00000110 or 00001001 after firing order is complete (only last 4 bits are used). A "1" bit equals 5 volts and a "0" bit equals zero volt. This bit pattern can be read on scan tool as CALC. COMPRESSION OUTPUT. If bit pattern 00000110 is detected, ECM is syncing engine on TDC compression cylinder No. 2. If bit pattern 00001001 is detected, ECM is syncing engine on TDC compression cylinder No. 3. DTC sets when ECM detects no change in cam signal input for a certain number of engine revolutions during engine crank or initial start.