Tag Archives: diagnostics

Golf / Jetta TDI with DPF and boost faults.

This Volkswagen Jetta came into us with its engine management light, DPF light and glow plug light illuminated. It had very little power and needed some attention.

Firstly we carried out a diagnostic code read to see what fault codes were causing the light to be on, several codes relating the Diesel Particulate Filter (DPF) being blocked or soot content to high and one relating to boost pressure lower than expected.

Next we tried to clear the codes and restart the car to find out which codes stayed live, in this case all the codes stayed.

We tried to carry out a Diesel Particulate Filter Regeneration which with this particular car has to be done whilst driving.

You have to drive the car in 4th or 5th gear at approximately 2000 rpm until the DPF light goes out, this can take up to 40 minutes depending on how blocked the DPF is.

The regeneration did not work, so back to the workshop for some more tests.

We tested the differential pressure before and after the DPF, this is done using a pressure gauge which is connected on to the pressure sensor pipes, if the pressure is to high the DPF wont allow you to carry out a regeneration and the DPF will need to be cleaned out using chemicals either on or off the car.

The DPF soot content on this Jetta was very high so we decided to remove the DPF and have it chemically cleaned.

DPF removed from car.

Whilst the DPF was off we decided to check in to why we were getting a code for low boost pressure, we checked the turbo actuator pipes for leaks which all seemed ok then we checked to see if the actuator was working using a vacuum tester, the actuator wouldn’t hold vacuum.

We removed the turbo actuator and tested it against a new one (see the video below)

Once the DPF had been cleaned out and we had replaced the faulty turbo actuator it was time to retest the the car.

We cleared the codes and took it for a road test, all the warning light extinguished and we had full power, brilliant.

After speaking to the customer we realised that the car had lost power several months ago and he didn’t have it looked at until now due to the fact of not just one warning light being on but three on the dash.

The car wouldn’t carry out a driven regeneration of the DPF (which they do regularly under normal circumstances) due to the faulty turbo actuator which then caused the DPF soot content to increase until it was full causing all the warning lights to come on.

The Moral of this story is ‘Warning lights are important‘ if you have a warning light come on on your car get it checked out before it causes any more damage.

Aarons Autos car service garage.

Your friendly car garage in Derby

Give us a call at Aarons Autos for more info.

Citroen Berlingo with ABS Wiring Fault.

A 2014 Citroen Berlingo came in to us with an ABS fault to be looked at.

First thing to do was carry out a diagnostic code read to see why the ABS light was on, the particular code for this Citroen Berlingo van related to an open circuit on the rear left wheel speed sensor.

We checked the actual wheel speed sensor for a fault but it checked out ok, next job was to check the wiring from the sensor back to the ABS pump.

Most of the wiring for the rear ABS sensors is hard to access as it runs inside the van. once we had determined that there was in fact a break in the wiring from the left rear sensor and the ABS pump (by checking continuity of the wires) it was time to start stripping the interior and physically check the wiring for a break.

After removing the passenger seats and lifting the carpets to access the wiring we noticed part of the raised carpet flooring had been trapping the ABS wiring loom between a raiser and the body and over time had rubbed through the wiring and caused it to short out against the body.

ABS wiring trapped under the carpet.

We repaired the wiring and and rechecked for continuity through the loom which we now had. Time to clear the stored fault codes and check for a wheel speed signal using the live data on our diagnostic scanner, perfect, the signal was good and the same as the rear right wheel, time to rebuild and road test.

Aarons Autos car service garage.

Your friendly car garage in Derby

Give us a call at Aarons Autos for more info.