P0340

P0340 means the ECM is seeing no signal at all from the Bank 1 camshaft position sensor circuit, which on modern engines is the reference for variable valve timing closed-loop control and for sequential injection synchronization. On engines without a backup strategy, P0340 is a crank-no-start; on engines with limp-home logic, you get rough idle and a hot restart that takes 3-5 seconds longer than normal because the ECM has to find TDC the slow way. Cheapest-first ladder: scope the CMP signal during cranking and verify Hall-effect pattern (clean 0-5V square waves synced to crankshaft rotation at half speed). Unplug the connector and verify 5V reference and clean ground at the sensor with key on (anything less than 4.8V reference means an ECM-side feed problem, not a sensor problem). Inspect the cam reluctor target — on aluminum heads the target tooth can wear or get hit by a dropped valve spring keeper, and the tooth profile damage gives no-signal even with a good sensor. Check for oil intrusion into the CMP connector — chain-cover or cam-cover leaks routinely drown the CMP harness and pull the signal to ground through wet insulation.

Vehicle-specific patterns: VW/Audi 2.0T EA888 and EA113 (2006-2015 GTI, A4, A5, Tiguan) sets P0340 when timing chain stretch lets the cam drift far enough out of crank correlation that the ECM disqualifies the CMP signal — the fix is a chain, tensioner, and guides job, not a sensor. Honda K-series K20/K24 (2002-2015 Civic Si, Accord, CR-V, Element, TSX) suffers Hall-effect CMP heat-aging failure where the sensor passes spec cold and goes no-signal after 30 minutes at operating temp — extremely common at 120k-180k miles. Chrysler 3.6 Pentastar (2011-2018) throws P0340 when oil control valve screens clog with sludge from extended oil-change intervals and cam phasers cannot hold the commanded position, corrupting the CMP pattern. Ford 5.4 3V triton sets P0340 alongside P0016/P0017 when the cam phasers themselves fail mechanically. Estimated repair: $180 to $2400.