Electronic control unit software issues for heaters Webasto Thermo Top V and VEVO in Land Rover vehicles
Recently we have had an increased number of support requests and discussions on various forums related to some issues with the use of ALTOX GSM modules, so we decided to comment this situation.We would like to mention that this problem is well-known and researched by servicemen specializing in servicing of Land Rover cars, service technicians of electronic control units of pre-heaters and by us.The problems are the following:– Error 81 (EOL - checksum error) via WTT (Webasto Thermo Test) or via error reading request using ALTOX GSM module. (When diagnosing via Land Rover - control unit malfunctioning).– Error 22 (resistance error) via WTT (Webasto Thermo Test) or via error reading request using ALTOX GSM module. (When diagnosing via Land Rover - control unit malfunctioning).Error 81The common wording – "I installed ALTOX GSM module and it caused malfunctioning of the electronic control unit malfunctioning.Let's go through it point by point:- It is hardly possible to cause the malfunctioning of the electronic control unit physically, not to mention via WBUS that connects the module and controls the heater.- The recorded malfunctioning in these cases are failures of the control unit software that does not have a good protection. There are two types of that, both well-known by specialists who perform the recovery:а) use of ALTOX GSM module's functionalities that are not supposed to be used with heaters in Land Rover cars;b) unstable or low car supply voltage or the heater.Now let's talk about specific situations and the reasons that cause them:1. The use of the following functionalities of the ALTOX WBUS-4 GSM module (from the user manual):8, 9. Unblock Webasto T5GP (Т5) – SMS-commands heater_unlock1(2).These commands often are used by Land Rover owners despite the fact that:- For all Webasto heaters, including default heaters in Land Rover Freelander II, Discovery 3, Rang Rover Sport Error 7 Heating unit interlocked is just an error and can be removed by deleting! The exception includes Volkswagen T5 and T5GP vehicles. Here to remove Error 7 you need to write certain values in the EEPROM of the heater's electronic control unit. Then you will be able to delete the error.- The table states Unlock Webasto T5GP (Т5) which means that this functionality applies only to Volkswagen T5GP and T5 vehicles.When one of these commands is forced, the module - thinking that there is a default heater of VW T5 or T5GP - performs the unblocking procedure and writes certain special values in the EEPROM of the electronic control unit that are meant specifically for VW T5 / T5GP. Since the entered values differ from set values for Land Rover, this causes checksum error.Currently, despite the fact that the problems are caused by negligence or poor attention to detail by the users, this functionality has been excluded from the GSM module's software and will not be used in the future to the disadvantage of other users.2. Heater's Power Supply Issues Service technicians often have to deal with Error 81 on the cars that are not equipped with ALTOX modules, however, in some cases ALTOX module is indirectly involved into these issues. There are three types of situations when Error 81 appears because of power supply issues:- A very slow discharging battery. For example, in cases of a lengthy downtime;- A low battery capacity and the subsequent starting engine operations;- A low battery capacity and/or poor electric wiring to the heater when ALTOX GSM module is installed.As mentioned above, in the last case, the module is indirectly involved in the malfunction. It is used for the preoperational start of the heater, and because of the low battery capacity or poor wiring when the heater's pin or the internal combustion engine's starter is switched on, the voltage on the vehicle can reach a very low intolerable that causes the malfunction of the heater's software. Voltage fluctuations can be short-term and not measured by the household measuring devices. To avoid problems the following rules should be applied: do not use old batteries or low on charge batteries, the time of the ride should exceed the time of the preoperational heating, regular checks and possibly cleaning of the wires connecting to the battery and the heater should be performed.ALTOX modules are some of the very few modules that work on Land Rover Discovery 3 and Range Rover Sport, and are very commonly used, and that explains that the majority of trouble cases is attributed to this equipment. A half measure to prevent the malfunctioning of the heater's software on the car with power supply issues with the preoperational start control unit, can be switching off the heater before starting the engine, regardless of the heater's manufacturer. The heater shutting down time from the moment of sending the command to the engine start should be around 1.5 minutes, this is required to complete procedures and shutting down.Please note that Error 81 can't appear for the cars with charged battery and a normal condition of the heater's wiring!Error 22This error applies only to default Webasto heaters for Ford, Land Rover and Volvo vehicles and has no connection to ALTOX GSM module or any other controlling unit.- The cause of the error is related to the complex algorithm getting into which does not make any sense now. In simple terms, "the time has come." - This error can appear faser if the glow plug is degraded or was replaced. Service technicians can inform the car owner about that when restoring the electronic control unit.