Desk diagnostics

Sometimes, says Neil, the best place to start your work is online, in the various VM information portals

Published:  16 September, 2020

By Neil Currie

Is checking for manufacturer technical service bulletins part of your diagnostic procedure? Well, if it isn’t, it should be. Allow me to explain why with a couple of workshop scenarios I had recently.

The first vehicle was a 2008 Range Rover Sport. The customer’s complaint was that after leaving the vehicle sitting for a few days due to working away, upon his return the vehicle’s battery was flat. They had recently had a replacement battery fitted and the problem still occurred, so they wanted the vehicle checked for a battery drain.

After checking for a drain, I found a constant 1.2 amp current draw after allowing the vehicle to shut down. This was well above specification (30ma) for this vehicle, so it did indeed have a drain. In the past I would then start testing fuses and relays for voltage drop. Why voltage drop? You need to do it this way, as the old-fashioned technique of pulling a fuse and seeing if the draw disappears no longer applies. Nowadays, when a fuse is pulled which powers a module, it will wake up the network, which will have seen a module go offline. This then causes a drain. This can be very time-consuming, as refitting the fuse and waiting for the vehicle to shut down again can take 20-30 minutes in some cases. Also, depending on location and size of the fuse boxes, it can also take a long period of time to go through each, and sometimes this is inevitable though, and must be done.

Diagnostic process
Now, thanks to refining my diagnostic process, after gathering data I checked Land Rover information portal Topix. If it is another make of vehicle, I check their own information portal to see if it is a known issue or if a bulletin is present to aid me while gathering wiring diagrams and other information that I may need. I don’t want to spend a long period of time running through a series of checks to find nothing wrong to then find out there is a repair already recommended by the manufacturer to repair the issue. Again, been there, got the t-shirt.

This particular vehicle did however have a technical bulletin – LTB00215V3 (in case you want to have a read) for a battery drain. Reading the bulletin, it then went on to say if the presented vehicle had a constant battery drain of 1.2 amps the cause was the instrument cluster not entering ‘sleep mode’. Great, so straight away I have found a TSB and reading it will give me the fix, the bulletin said to repair the vehicle update the software in the instrument cluster, LR have released modified software to allow the dash to enter sleep mode and stop draining the battery.

After carrying out the update another test was carried out to measure the current draw and this time now was below 30ma confirming the complaint was fixed. Without finding this bulletin, I may well have gone around in circles. Yes, the fuse(s) for the instrument cluster would have shown voltage drop over them indicating the circuit was active. However, it may have  only pointed to suspecting the unit was possibly faulty due to being awake when it shouldn’t be, or another issue if the fuse fed multiple components.

This is commonplace now for one fuse to power two, three, four or even more components at once. So if this was the case it would then require more time to rule out each and every one to find the cause. Imagine spending hours removing trim panels and removing and refitting modules to find an update would have fixed the problem all along.

Hard acceleration
The second vehicle was also a Range Rover Sport. The customer’s complaint was that under hard acceleration, blue smoke was seen from the exhaust and under normal driving conditions all was fine. Again, this could be caused by a number of issues and where do you start? How do we prove it’s a worn engine, possibly piston rings? A failed turbocharger? The list goes on.

Both engine and turbo worked. To carry out any major engine and/or turbo work on this model access involves body removal. The main turbo is buried, so even accessing it to carry out some checks in situ is almost impossible.

 I checked the oil level and some other basic checks and all was ok so decided to check Topix to see if this was a known issue before diving in with both feet. There was a bulletin, LTB00487V6, which stated the issue was more than likely caused by ineffective draining of the secondary turbocharger. The bulletin also gave a list of primary checks to be carried out first. All were ok so the bulletin said to fit a modified drain pipe to the second turbo with instructions, part numbers and the replacement procedure and post fix information. After the work was completed the vehicle’s initial symptom was gone, indicating a fix. Imagine removing the body and inspecting turbochargers and pipework etc to find nothing wrong and then heading for the engine!

Maintain pressure
In my last example, I was able to help a fellow technician who had posted on a Facebook automotive group asking for some help with a Freelander 2. The vehicle was logging circuit fault codes for all four piezo injectors and wouldn’t start and then other times run and cut out. He had tested all four injectors electrically and they had passed all tests. He then checked the wiring between the engine control unit and injectors and again everything was ok which only appeared to leave a control unit fault.

Another ECU was sourced and fitted and the fault will still present, much to his dismay. After further checks he decided to post on the group asking for some help and where he could be going wrong. It was at this point I decided to check for a TSB. Lo and behold, there was one for the fault code he was experiencing (LTB00277v2). The bulletin stated that this engine uses a 10-bar check valve in the fuel return pipework to maintain pressure on a hydraulic chamber inside the injector itself, which was critical for correct injector operation.

It was possible, due to poor quality of fuel, wax or ice could form blocking the 10-bar check valve. This restricts the returning fuel leaving the injectors and causes the pressure to rise to over 150-bar. This in turn deforms the piezo actuator within the injector causing an electrical short to ground internally in each injector all at the same time. Some tests were done with this new-found knowledge and the valve itself was indeed blocked.

A new leak-off pipe assembly was fitted and the vehicle was fixed. Imagine where the job could well have gone if this information had not been found again reinforcing what I have mentioned in this article.

Printing and reading
The wealth of knowledge and information that can be gained from manufacturer portals nowadays is brilliant. A lot of my learning has been doing by spending time printing and reading system operation and descriptions of different vehicles to get a better understanding of how it all works.
    
This also includes known faults, as seen here, to save time when a vehicle comes into the workshop. Most websites are under £10 an hour to access, so well worth it in my opinion. The only downside can be navigating them all, as no two are the same unfortunately. While there you can also get factory wiring diagrams, service schedules, workshop manuals, technical specifications the list really does go on so next time you have some spare time or are struggling with a fault, consider signing up to one and do some self-learning or check there isn’t a bulletin available for the fault you have.



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