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Case Study: Camshaft Sensor Error

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Master Technician George Cramer at Blackpole Autocentre in Worcester, follows good diagnostic procedures to save a customer the cost of an unwanted camshaft sensor replacement.

Figure 1

George was handed a workshop job card for a 2014 Vauxhall Astra2.0 A20DTH Diesel. The Engine Management lamp was on and the vehicle was suffering from occasional poor starting, excessive cranking time and limp home mode. “It was an intermittent fault, so most of the time the vehicle ran fine,” says George but he connected his Delphi DS150 so the fault code was live – P0340 Camshaft position sensor. By pressing the ‘!’ button within the fault code he was able to see if there were any common faults with this fault code, on this occasion there were no known issues. The next step was to access the Cam sensor, luckily this is easily accessible on the A20DTH engine and its location was pulled up on the Delphi VTI (Vehicle Technical Information) software, see Figure 1. 

Figure 2

Suspecting that the sensor had already been replaced (it looked new), George wanted to investigate further before replacing the component. Again, using the VTI, George was able to view the wiring diagram and follow the test procedures. This particular engine uses a Hall Effect Sensor for the Camshaft Sensor. This meant that the sensor required a negative and 5-volt feed, which meant the sensor could develop a 5-volt square for the ECU, see Figure 2 (Pin 1 = 5 Volt ECU supply, Pin 2 = Signal from sensor to ECU, Pin 3 = Negative from ECU). 

He first checked power and grounds (Pin 1 and 3) using a standard multimeter. Everything checked out OK, there was a good earth and 4.5volt power supply. Still suspecting a wiring issue, George decided to use the Pico Oscilloscope, to give a full picture of what is going on, when compared to a voltmeter. 

Looking at pin 2, the signal wire, everything looked fine so he decided to scope pins 1 and 3 power and ground, just in case there was a loose connection or poor wiring which couldn’t be seen using the multimeter. 

Figure 3

After several checks on pin 3 (5 volt power supply), George found that the supply voltage was consistently changing; so he conducted a wiggle test on the connector and wiring and discovered that the pin was not correctly located within the socket of the connector, see Figure 3. 

Carefully removing the pin within the socket, George discovered that the issue was a simple bent securing pin – this was an easy fix. He straightened and refitted the securing pin and reassembled the 3-pin plug. To confirm the fix, George decided to carry out another wiggle test using the oscilloscope. This confirmed that George had a reliable 5-volt feed; and could clear the fault codes using the Delphi DS150. Job done! 

Equipment used: 

• Delphi DS150 

Access to Technical Data, VRM lookup, Service light reset, Read/erase fault codes, Read /graph live data parameters, Full vehicle ECU scans, Programming, Component activation/adjustment, ECU coding etc. 

• Pico oscilloscope 

• Delphi VTI (Vehicle Technical Information) Ultimate Pack 

This is integrated into the DS software, making easy access from diagnostics to technical data; used for component location, wiring diagram and test procedures. 

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