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P0340 Fault in 1999 Mercury Villager: Cam Sensor Issue and Hot-Engine Symptoms

Model: Mercury Villager Fault Code: P0340 Posted: 2007-07-24 08:48

I own a 1999 Mercury Villager with 171,000 miles and has been well maintained. The vehicle is throwing fault code P0340, indicating a camshaft position sensor malfunction. The issue only occurs when the engine is hot—typically after prolonged idling or frequent city driving cycles—and does not appear on cool days or during rain. I've already replaced the crankshaft position sensor (which was initially suspected as a secondary cause), at a cost of $28, and all wiring connections appear intact. The 1999 Mercury Villager uses an optical camshaft sensor that is integrated into the distributor assembly—this sensor relies on a precisely aligned plate with 360 small openings to detect cam position. The sensor is screwed in place and can be removed, but it's not listed separately in most parts inventories; only full distributor assemblies are available from dealerships or aftermarket suppliers (even from Ford). My concern: Is the issue truly due to a failing camshaft sensor, or could other factors—such as worn distributor shafts, misalignment of the sensor plate, or degraded electrical connections—be responsible? I've read that cleaning the distributor, sensor plate, and internal components may help, but I'm unsure whether dirt or debris would only cause problems under high engine temperatures. Before replacing the entire distributor assembly (which costs around $330), I'd like to confirm if there are any other diagnostic steps or overlooked causes. The code persists specifically when the engine is hot, which aligns with known behavior of both crank and cam sensors in older GM-style systems. Given that the crank sensor has been replaced and no other symptoms exist, I'm leaning toward a failing cam sensor—but I want to be certain before proceeding.

Related fault codes
P0340
Comments (9)
Anonymous 2007-07-24 11:32

You're planning to replace the distributor assembly next—does that mean you've ruled out other causes like sensor misalignment or dirty components?

Anonymous 2007-07-24 11:49

I replaced the crankshaft position sensor based on a parts store reference manual, which listed it as a potential cause for P0340. However, I can't find a standalone cam sensor for this model—only full distributor assemblies are available. I'm looking for alternative diagnostics before replacing the distributor. I've heard that cleaning the distributor plate and internal sensor might help, but would dirt only affect performance under hot engine conditions?

Anonymous 2007-07-24 14:41

If there's a crankshaft sensor and the distributor contains a camshaft sensor, then it's likely the distributor assembly itself is housing the cam sensor—so your issue may be tied to that unit.

Anonymous 2007-07-24 15:00

Apologies for the earlier error—I meant to say the camshaft sensor is located inside the distributor. It’s an optical type with a plate featuring 360 tiny openings aligned precisely with the sensor. The sensor is secured by screws and can be removed, but it's not shown in most parts catalogs. The alignment between the plate and sensor appears critical—field adjustments may be difficult or impossible without proper tools.

Anonymous 2007-07-24 16:03

Have you checked with the dealership for a separate camshaft sensor listing? It might be available separately, or you could potentially purchase just the cam sensor plate as part of a distributor assembly.

Anonymous 2007-07-24 17:58

Correct—both dealerships and aftermarket suppliers do not list the camshaft sensor separately. Only full distributor assemblies are offered. That’s why I’m trying to eliminate other possibilities: wiring is fine, crank sensor has been replaced, and symptoms only appear when the engine is hot.

Anonymous 2007-07-25 07:20

Since the P0340 code appears under hot conditions—common for camshaft or crankshaft sensors—and since the crank sensor has already been replaced, I’d recommend trying a used or new distributor assembly next. Without a scope to verify the signal, unless there’s actual cam timing misalignment, it's likely the distributor unit is at fault.

Anonymous 2007-07-26 06:43

I just replaced the distributor with a remanufactured unit from a parts store for about $330. So far, everything seems to be working fine—though weather has been cool and I haven’t yet created the high-temperature conditions where the original issue occurred. The problem usually happens when my wife drives, so I’ll know in a few days if it’s truly resolved. Thanks for all the input!

Anonymous 2007-07-26 09:32

Let me know how it holds up—based on what I’ve seen, this fix seems likely to resolve the issue permanently!