IMI Magazine

IMI Magazine


Diagnostics – could ‘Pass-Thru Programming’ be the answer?

Independent garages that invest thousands of pounds in diagnostic equipment in order to offer a complete all-makes service to their customers are continuing to be frustrated, reports James Dillon.

It is widely but rather grudgingly accepted that no one diagnostic tool will perform all the required tasks. Some provide broad coverage but shallow functionality, and others provide the opposite. The conundrum facing many independents is should they bother to offer diagnostic services at all? Should they spend a small fortune on multiple scan tools or become brand specialists and buy the tool which best suits the brand(s) they focus on?

Becoming a brand specialist using an aftermarket tool may be a step towards the authorised repairer model for the independent garage. However, it doesn’t necessarily mean that their diagnostic problems are solved, because certain critical diagnostic and repair functions are still the sole domain of the franchised dealer.

Troublesome Trouble Codes.Take for example a run of the mill 2001 1.8 Vauxhall Vectra with its X18XE1 engine. A recommended course of action for one of these vehicles when it shows an EOBD trouble code P0602 is to re-programme the ECU. This is done by updating the ECU’s EEPROM (Electronic Erasable Programmable Read Only Memory) via the vehicle’s diagnostic connector, using the dealer’s diagnostic tool. For most independents this means directing their customer back to the local dealer, or covertly sub-contracting the repair work to the dealer.

Other vehicle faults that may not actually exhibit a trouble code, such as poor engine driveability, vibratations or stalls at drive off, can be cured by updating the ECU’s engine control programme with a newer version, which is available only to the dealer, and can only be programmed by the dealer.

To date, no aftermarket tool has the reprogramming functionality. With this in mind, one train of thought is that the independent should forget aftermarket tools altogether and opt for a bank-busting dealer tool. It is possible to buy dealer tools, although it rather depends on the manufacturer in question.

For example, the GM tool, Tech2, can be bought through a rather convoluted personal import procedure from Europe or the US. However, getting the security HASP (or Hardware Key) to unlock the tool’s full functionality is not quite as easy. The GM tool has a market price of around £2,500.

For those wishing to specialise in the Land Rover range, the T4 tool is available on the open market from Omitec Instrumentation. The T4 costs over  £9,000! Other dealer tools are also available, but may be more difficult to obtain.


Effectiveness of EOBD

This calls into question the spirit and effectiveness of EOBD. The whole reason behind this legislation was to enable a suitably equipped (those garages with an EOBD tool) to fix emission-related problems on any make of vehicle through a common socket, using common protocols, common diagnostic routines and common fault codes and information.

EOBD was introduced to ensure that no undue pollution of the environment took place whilst the vehicle driver travelled for many miles with a fault to find his dealer. All repair shops had the ability to affect a fix. This may now not be the case.

Pass-Thru ProgrammingWith the reprogramming of ECUs to solve vehicle running problems the exclusive domain of dealers, the environmental benefits of EOBD are severely reduced.

The US Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) have proposed requirements for reprogramming vehicles for all manufacturers by the aftermarket repair industry. The SAE has developed this requirement into a standard, J2534, which deals with a ‘Recommended Practice for Pass-Thru Programming.’

In essence, the recommended practice provides the framework to allow reprogramming software applications from all vehicle manufacturers and the flexibility to work with multiple vehicle data link interface tools from multiple tool suppliers. This system enables each vehicle manufacturer to control the programming sequence for ECUs in their vehicles, but allows a single set of programming hardware and vehicle interface to be used to program modules for all vehicle manufacturers.

This standard does not limit the hardware possibilities for the connection between the PC used for the software application and the tool (e.g., RS-232, RS-485, USB, Ethernet...). Tool suppliers are free to choose the hardware interface appropriate for their tool. The goal of the standard is to ensure that reprogramming software from any vehicle manufacturer is compatible with hardware supplied by any tool manufacturer. The standard is intended to meet those proposed requirements for 2004 model year vehicles. Additional requirements for the 2005 model year may require revision of the standard.


The Answer?

Details of compliance to the standard are being reviewed by the NATSF. This US based organisation is a not-for-profit, no-dues task force established to facilitate the identification and correction of gaps in the availability and accessibility of automotive service information, service training, diagnostic tools and equipment, and communications for the benefit of automotive service professionals.

Its equipment committee reported during March 2003 that ‘Reprogramming is a little confusing at the moment’…first of all there are a few problems with J2534 that have to be worked out.  J2534 is not based on current practice; it is based on a document and therefore is:

Highly subject to interpretation by OEMs and scan tool companies. There are known ambiguities in the specification and there are probably more that have not been discovered. There will be implementation errors and discrepancies by OEMs and scan tool manufacturers alike. These errors will be worked out with time as they always are. OEMs and scan tool manufacturers need more time to implement J2534.  2004 model year vehicles are almost here.  The equipment committee is recommending a delay in implementation while leaving model year requirements alone.  How long the delay needs to be worked out between regulators and experts within the J2534 Committee. 

In addition to this there will still be large amount of non-emissions related programming that will NOT be covered by this standard. The NATSF reports that ‘although J2534 is required for emissions-related reprogramming beginning model year 2004, non-emissions reprogramming does not require J2534’. 

This means that the aftermarket could still have to purchase proprietary OEM tools in order to reprogram certain modules.  Some OEMs do not use J2534 protocols for non emissions-related reprogramming.  Two well-known protocols are Ford’s UBP and GM’s single wire CAN.  How do these manufacturers plan to supply reprogramming to the aftermarket under the letter of intent?

As far as the UK goes, it is as yet unclear if the EU has any legislation in the pipeline to deal with this matter, but watch this space.

Back to the independents’ conundrum of offering diagnostic services or not – it seems as if the goal posts have moved further up the un-level playing field.