13 Jul 2024
The voice of the independent garage sector

A month in the life of a vehicle technician

I left off last month with the problems that poor parts choice create and how this affects a professional and efficient repair. A remarkably similar experience occurred this month, following a simple requirement for a brake master cylinder swap-out on a Volvo XC60 2.4 diesel from 2016 with 60,000 miles on the clock.
A hydraulic leak dictated a new replacement. This awkward-rather-than-challenging task was competently conducted by one of our workshop techs. Following the repair, the owner was experiencing the vehicle alarm going off. My first task was to conduct a battery test. The main service battery was fully serviceable; However, the auxiliary battery had a blown 70amp control fuse.

Once replaced, the next problem was a loss of comms with the central electronics module U014000. Further examination of serial data with TOPDON indicated no response from the brake pedal switch. This switch uses a Hall Effect position sensor, as do most brake and clutch pedal sensors. The sensor was fully evaluated with my scope, confirming no change of status. I established that the new master cylinder was not supplied with a sensor pre-fitted. Instead, there was one that had been supplied by a well-known national discount parts supplier, based on low-cost. Here we go again…
Passing a small magnet across the Hall Effect IC should prompt a response across the Hall gate, which it did. So, the sensor was operating correctly. Further enquiries from the so-called supplier’s technical support team confirmed that the correct master cylinder was supplied despite there being two distinctive options; Stop and non-stop/start. Further examination confirmed the internal hydraulic piston had no phonic generation element. Fitting a genuine part cured all comms and service errors. It even came with a new Hall sensor.
My next task was more conventional in nature relying on experience, process, and accurate data, it did however expose my total lack of Renault product knowledge. The vehicle was a Renault Captur Dynamique, 1.5 diesel 2014 with 35,000 miles on the clock. It all began with an intermittent SRS fault indicated as drivers squib circuit. I also noted that the cruise control switch was not operating. I cleared all codes and advised a second opportunity to confirm if it reoccurred which it did. Pretty straightforward advice and choice here; It was the clock spring. Due to impossible test opportunities in service, a new unit was recommended.
Swapping out all the trim exposed the possible cause of failure; Extensive cigarette ash within the steering housing. There are several electrical sockets within the housing controlling most of the lights, wipers, cruise control. These were electrical lube-cleaned and complimented with a new clock spring. Fault fixed.
This was shortly followed with a battery charging fault. The vehicle would charge normally for a brief period then the generator light would illuminate. The wipers would then operate without request and could not be terminated until the ignition was switched off.
As I only work three days per week (perks of seniority, in every sense), a new alternator had been fitted by the shop with no change in status. The Renault employs smart charging technology, so my focus started right there. Smart charge systems rely on digital alternator exciter control. This was not present when scoped, only a flat 10v reference was present.

Fault codes confirmed the area of responsibility, df002, alternator control unit, df003 main system voltage, df0047 battery sensor voltage value out of range. Additional serial data indicated a starter relay, and wiper stalk fault. My next challenge, wiring schematics. E3 did support the system schematics, so off we went. Pin ID references did not check out, however wiring colour did seem to be accurate. Please refer to Fig.1.
I chose to disconnect the battery sensor and E6, the battery supply control unit, then conduct continuity tests through the loom. My first test points were at each extreme of the battery sensor circuit. Result open. Next, I broke down the circuit, from the battery sensor to a connector under the dash on the nearside. Result; 2 ohms, so ok. Please refer to Fig.2.
From the exit of the socket to battery sensor, result open, so the connector was faulty. I then chose to construct a simple bridge circuit to bypass the socket. Result; Smart charge control back online. So, the alternator puts out the 10v. This is modified to a digital charge control signal within the power supply module, thus proving a good module. The connector is quite a high-tech design, and relies on a mechanical zero stress engagement principle. The pins are incredibly small and fragile, so my only option was to cut the circuit on entry and exit then solder together. The alternator now charges normally, the wipers operated normally when requested via the control stalk, and all DTCs cleared. Please refer to Fig.3.

Soft master vs. hard master
So, what was my performance assessment? I’m a hard master, but pragmatic enough to identify where the problems existed. There was not quite enough data on E3, but a little visual assistance from the Google wizard to identify the various modules  helped. Try eBay for second-hand units. You will get quite clear photos to assist location and identification. See, I’m a softie when it comes to helping you lot. More next issue.