Computer diagnostic procedures / problems
A computer diagnostic test is a non invasive diagnostic procedure much like an x-ray or an mri scan. The test may be inconclusive and further investigation/testing may be required at additional cost.
A computer diagnostic test involves downloading stored trouble/fault codes stored in your vehicle's computer/electronic control unit (ecu). This information is accessed via a computer monitor screen and printer, and can only report data stored. Therefore, if a fault is recorded in your vehicle's computer memory we have to believe that it is correct. Unfortunately the stored information is not always a correct/accurate diagnosis of the vehicle's problem and only points us in a general direction. In some cases the vehicle's ecu can give misleading/wrong information codes, or ecu may be faulty itself. Problems can occur when your vehicle's "mil light" is on, and the vehicle has a misfireor jerking problem. The computer reports/diagnoses a fault with a particular part/unit. The unit/part is replaced and the "mil light" is now extinguished, but the original misfire/jerking fault is not cured, this can happen even though the computer reports the fault is no longer present/stored in the ecu. There may be a wiring, ecu fault, intermittent or underlying problem not apparent at the time of testing.
The above information is explained, and print-out copy given to the customer before any diagnostic work is carried out. The customer must instruct/authorise us to act on the information supplied by the ecu. If diagnostic testing is inconclusive, further electrical investigation or repairs / replacement parts that are most likely to cause the problem can be replaced. We cannot be held responsible if problems persist after parts are replaced and work is carried out. Further in depth electrical checking/work can be carried out if replacing ecu diagnosed parts proves unsuccessful, this repair is additional to the existing repair (current labour rate on web site), and can be very time consuming, customers are advised of vehicles progress at hourly intervals
No electrical parts fitted can be returned for credit.
Diagnostics/fault finding, using donor cars
The only other way to diagnose problems without occurring parts cost is by substituting parts from a donor vehicles, ie trial and error. This is usually easier and quicker at a main dealer due to the amount of identical cars on site. And some times it can also keep labour costs down. Occasionally when computer diagnosed replaced parts have not cured the original problem and other cheaper options have been explored, rather than pay for expensive further electrical investigation it may be more cost-effective to take the car to the main dealer as the ground/foundation work will have been done and the main dealer can concentrate on other causes.