Rover 75 Case Study
Had a Rover 75, 2004 plate 2.0l TD brought into the workshop with a intermittent non start fault and a general lack of power. Using a scantool I retrieved the following fault codes:
P3505 Glow System
P1260 Delivery fuel pressure monitoring
P0480 Cooling fan circuit
P0100 Air mass sensor
P0400 EGR control or EGR actuator
P1195 Rail pressure control valve
P1E25 Speed sensor monitoring
I decided to battle with the P1260 and P1195 codes first and see if there was any fault apparent.
Looking at live data I had a pre supply voltage PID but no rail pressure PID. Time to get scopeing
Using four channels I decided to check the signal voltages of the rail pressure sensor (channel a, blue line), the delivery pressure sensor (channel b, red line), pre supply pump amperage (channel c, green line) and starter current to show when I am attempting to crank/start the vehicle (channel d, yellow line).
The waveform below shows on the first crank there was no amperage draw from the pre supply pump, note the rail pressure voltage and the pre supply sensor voltages do not rise much also. The second crank the pump draws a amperage and the vehicle does start and run noting the rise in pre supply sensor and rail pressure voltages. See waveform below:
From that waveform I decided to test the pump supply voltage, earth and amperage in more detail just with ignition on, the feed and earth appear good but the pump rotational amperage is in a rather poor state. See waveform below:
It is now clear that a new low pressure pump is needed, I fitted a new non genuine one supplied by the customer (its his car so his choice) and the car is indeed fixed, performance is good and starts every time, took a similar waveform as above but of the new pump:
As can be seen that looks more healthier, average amperage is good and the speed is good showing the pump is turning freely.
With this we cleared the codes and took for another road test, some codes returned but the lack of power and intermittent no start is fixed, we now have one happy customer.
This just illustrates that even though I did not have all the scantool live data, the Picoscope clearly showed what was wrong and made the diagnosis accurate and rather quick with no guesswork.
psdata files attached in next post