Summer season is here
With the weather getting warmer we are starting to see more cars with A/C issues. Here is a Peugeot RCZ […]
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Renault Trafic non runner. Been at previous garage for 2 weeks without success. The immobliser light was flashing normally with ignition off, when switched on the red light would illuminate permanently without flashing, signifying a communication error between modules.
In Renaults wisdom to gain access to the UCH the dashboard has to be removed. Once access was gained we can then check continuity between different components. With accurate wiring diagrams a diagnosis can be achieved.
In the engine bay the ECU was exposed and the wiring loom stripped so continuity could be checked, where it was found that the canbus line between the UCH and engine Ecu was open circuit.
Now it was a case of tracing the correct wiring back to the UCH to find the break.
A simple repair was made to the wiring and the van ran fine.
A very happy customer picked up his van within a couple of days and could get back to work.
Into our workshop was this KA which had the problem of the hazards going off randomly whilst driving and wouldn’t stop until ignition is switched off.
We first disconnected the hazard switch but fault remained.
We then removed glovebox to reveal the GEM unit. To gain access to the plugs you have to remove the security cover. 
Once access was gained and the plugs removed the trouble was obvious
The car had previous bodywork done on the front and more signs of water were found in the scuttle
The customer was lucky in that the water hadn’t got inside the GEM unit so with a good clean all was well.
This car had intermittent power steering issues. A quick diagnostic code read revealed ecu issues
Access to the module is good so it’s easy to check the wiring to the power steering unit. There is a big feed and earth and then 2 signal wires (canbus) all ok
A new power steering unit was sourced
Removing the unit is ok, but getting the unit out requires loosening the whole subframe to make enough room.
Rusty nuts and bolts can be an issue, but with perseverance and experience another successful job and a happy customer.
came into our workshop with intermittent mil light illuminated.
Honda cars are usually very reliable
A diagnostic code read found a fault stored on the VVT SYSTEM.
The VVT system is operated via a valve on the back of the engine that is oil pressure operated. The wiring to the valve was tested and found to be ok.
The customer when questioned further had said that the oil light had been flashing on occasionally. The oil was checked and found to be comtaminated. This in turn can block up the valve which has a fine gauze internally to filter the oil.
This is the valve with the gauze removed
With the valve removed and stripped the gauze was found to be blocked
With the valve cleaned and refitted, a engine flush and new oil and filter. The car ran fine and with no expensive parts required a happy customer picked up his car later in the day.
This Golf was brought in with a variable discharge on it.
After initial checks the discharge was found on the power distribution module. The module was found to be staying live and not switching off.
The problem is this module controls all the auxiliaries on the vehicle so the fault could be on any one of several circuits. Through proven diagnostic processes and much testing the fault was traced to the drivers door where the Cambus wiring had shorted to positive.
Not a common problem and one that can be very difficult to find
This car arrived at our workshop as a non runner. Various other garages had tried to get to the bottom of the problem without success.
It was dead on the key, so the starter circuit was the logical place to start. All fuses and connections were tested first, all proved ok. A serial scan came back with communication and canbus issues and we couldn’t communicate with the engine Ecu at all.
Accurate wiring diagrams are essential and it was found that the Starter motor is fed from the ecu. Access was gained to the ecu so we could check supplies and earth’s. Several supplies were missing.
Theses supplies came from the main ignition relay. This relay is a switched negative, this negative supplied by the ecu. So it seems that the ecu receives the signal from the key, it accepts the key if correct then trips this relay to wake up the rest of the ecu.
So now it was a case of tracing this wire from the ecu to the relay. After some stripping and probing 3 breaks were found in the loom, 2 near the ecu which in these cars are situated low near the wheel arch and can be susceptible to water damage if the plastic guards get damaged. The other break was in the engine loom underneath the battery tray again where it can be exposed to the weather.

This is the break under the battery tray
The breaks near the ecu seen here above the ecu plug
A second Scenic into our workshop this week with electronic handbrake trouble.
A quick diagnostic code read brought up fault codes saying internal ecu fault. To confirm we removed the plug from the module and checked the pos and earth feeds and the canbus signals. All proved correct.
The motor was removed and a new unit sourced and fitted.
It then has to be coded into the car. 
This fine example of the C63 came in via another garage with headlight trouble.
The wiring to the lights was checked first as to gain access to the bulbs and hid controllers the bumper has to be completely removed.
The wiring was found to be ok so with the bumper removed we tested the bulbs and controllers
the testing found one of the HID controllers to be at fault. An o.e unit was sourced, another happy customer.
Into our workshop this week was this BMW which had a problem with the wipers not working at all. We Firstly checked and confirmed all fuses were ok. Then we gained access to the motor which isn’t the simplest of jobs on this car, again the motor proved good. Using accurate wiring diagrams the next thing to check is the control relays which again are not easy to access having to remove 3 modules to gain access.
Once we got to theses relays the fault was obvious, the relays were in a well that was full of water and this had corroded the relays and bases.
New parts fitted all wiper functions returned.
This Ford was brought in to us with intermittent non start issues. When the fault was apparent it was dead on the key and the immobliser light flashed quickly. Through experience of these faults we knew this signified that there was a communication issue between the GEM module and the ECU in the engine bay.
Accurate wiring diagrams and test procedures are key to finding these kind of faults. Through proven test procedures the fault was traced to a damaged plug in the engine bay. The plug repaired and a test drive later all was well
