Pulling Codes: Signal No Longer Detected, The Story of Code P0340 – UnderhoodService

Pulling Codes: Signal No Longer Detected, The Story of Code P0340

Figure 1
Figure 1

This article will document the infamous P0340 code — Camshaft Position Sensor Circuit Malfunction. This is a code that involves the CMP signal, and, in many situations, one may be tempted to replace the sensor right away. This article will attempt to provide a game plan of attack.

It’s always wise to start with a schematic of the system you are working on. See Figure 1.

Our subject vehicle is a 1999 Ford Windstar. The camshaft signal on this vehicle is used per the PCM to control injector timing. This vehicle has a rough cold start, but does start immediately. It appears to have multiple cylinders that are misfiring.

Figure 2
Figure 2

Our first step is to verify the complaint by checking the system with the EASE software, a PC-based system. It confirms we have a P0340 stored in memory. Let’s review the freeze-frame data and misfire data. See Figure 2.

Freeze-Frame and Misfire Data:

Engine Coolant Temperature: 45°

RPM: 1,854

Fuel System Status: closed loop

Total Fuel Trim Bank 1 (ST+LT): 15.59%

Total Fuel Trim Bank 2 (ST+LT): 8.64%

Vehicle speed: 0 mph.

Figure 3
Figure 3

The freeze-frame data shows that each bank has a tendency to run lean. A gas analysis is performed to ­confirm what we suspect. Review the following five-gas analysis code software data screen (Figure 3).

Figure 4
Figure 4

The gas analysis shows that the ­vehicle exhibits an optimum air/fuel ratio. It’s very difficult to see the fault per this five-gas analysis. A test drive was performed on the vehicle to gather additional data, and the snapshot showed that there was indeed misfire activity at times. See Figure 4.

A valuable clue soon surfaced; the cam sensor synchronizer was making a squealing noise. At times it was very noticeable, but at other times you could hear only a very slight noise.

Figure 5
Figure 5

The cam sensor was then scoped (Figure 5). The following pattern (Figure 6) is what we saw.

Figure 6
Figure 6

The pattern in Figure 7 appears to be good, but we have learned over the years to always wait to see if there is more to the story. Our patience pays off; we start to see what the problem may be. SeeFigure 8.

Figure 7
Figure 7
Figure 8
Figure 8

The cam sensor was then taken out for a visual inspection (Figure 9). It was found that the cam sensor synchronizer was very hard to turn.

Figure 9
Figure 9

The cam sensor synchronizer was replaced and the driveability problem was resolved.

This Pulling Codes case is now closed.

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