European diagnostic paradox, The

Motor,  Mar 2002  by Jonsson, Kerry

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Can you count on your fingers and toes the number of European vehicles you've seen in your shop in the last six months? If the answer is Yes, then you probably figure you're not up to speed on the best way to diagnose problems when a late-model rolls in.

Late-model European vehicles may have a warning light-or a whole bunch of 'em-you're not familiar with. You don't want to spend hours checking this, that and the other thing, only to find you can't get into self-diagnostics without a scan tool. On the other hand, you don't want to send those customers to the shop down the road, either.

Well, here's some information to help you along. On the following pages you'll read which European systems are computer-controlled, which you can access without a scanner and which ones require a proprietary scan tool. This will let you know if a processor has turned on a warning light or if it's just a manual switch. It'll also help you realize what you're getting into in the way of time required for diagnoses, and afford your technicians the same courtesy.

The eight nameplates we'll cover are (in alphabetical order) Audi, BMW, Jaguar, Land Rover, Mercedes, Saab, Volkswagen and Volvo. Let's get started. Audi

Starting with its 1985 models, Audi's engine management systems have self-diagnostic capabilities. Previous to that, diagnostics are handled by simply checking the inputs and outputs directly at the engine ECU. Engine management faults, which cause the CEL (Check Engine light) to illuminate, can be diagnosed through self-diagnostics on '85 through '94 models. No special tools are required here; just a couple of jumpers and a homemade LED test light get you to blink out codes. Refer to your repair manuals or CD-ROM-based information system for the particulars.

Unfortunately, in 1995, self-diagnostic procedures using this method were removed on all Audi vehicles except the S-series, which retained the "blink code" method. On all other models, if you want to use any of the self-diagnostic functions, you'll need a scan tool that's the equivalent of a VAG 1551/1, 2 or 3. Of course, all this became moot in 1996, when OBD II regs came on board.

Audi started computer-controlling its automatic transmissions in 1994 on its high-end vehicles. Diagnostics for this system supposedly has blink code capability, but I have never been-nor have I heard of anyone who has ever been-successful at pulling codes this way. Once again, a scan tool is the weapon of choice.

The same goes for Audi's ABS systems. Be aware that the Servotronic brake and power steering systems used on some vehicles have electronic controls but no self-diagnostic capabilities. SRS systems have self-diagnostics, but require a scan tool to access the data.

In the mid-'90s, Audi started adding self-diagnostics to the instrument cluster and traction control systems, which were available on some models. Like most everything else with Audis, you'll need a scan tool to access the info.

Audi climate control systems have always had a self-diagnostic function, and while a scanner is nice to have, its not an absolute necessity. Up until the '97 models, you can use the control panel to access faults in the climate control system. Once again, refer to your repair manuals or CD system for the specifics. It's quite apparent that despite OBD II, there's still a need for a proprietary scan tool to access most of Audi's late-model computer systems.

BMW

If you see an illuminated CEL on a pre'96 BMv, you needn't worry. Five stabs at the gas pedal and the engine ECU will spit out codes. On 12-cylinder models, stomp on the pedal six more times to get codes from the second control unit of the split system. Once OBD II regs kicked in, however, these options were eliminated, with scanners the only game in town for accessing engine management system faults.

Since the 1990 model year, BMW has added many other computer-controlled systems, and every one of them requires a scan tool to tap into self-diagnostic functions. These systems include transmission control (EGS), anblock brakes (ABS), stability control (ASC), traction control (+T), cruise control, electronic throttle (EML), air bags (SRS), electronic suspension (EDC), etc. Body control modules were added in the late '90s and, you guessed it, require a scan tool, as well.

Jaguar

Fuel injection system diagnostics have been available on Jags since 1986 for its 12-cylinder two-door models and since '88 for sedans, both through the control panel. This method was retained on both models through the '95 model year. A year later, OBD II regs kicked in.

A scan tool is required for transmission diagnostics for all pre-OBD II Jags. Steering and suspension system problems are straightforward repairs; nothing fancy here. You can also access ABS self-diagnostics without a scanner on 1989-94 XJSs and 1990-94 XJ6 models by jumping the diagnostic connector and getting codes to spit out. After '94, a factory scan tool is needed for ABS work.

Beginning in the mid-'90s, Jaguar allowed self-diagnostic information for the climate control system to be accessed through the control panel itself However, starting with '88 models, all other systems that have self-diagnostic capabilities, such as the SRS and body control systems, require a scan tool interface.