Porsche Electronics Specialist

Cambridge, England

'The Spanner' - Diagnostic Tester for the Porsche 928

The Spanner - Porsche Diagnostic Tester


The JDS Porsche Diagnostic Tester is an enhanced flashing code tester for ECU fault code reading, clearing fault codes, idle adaptation, and digital dash diagnosis on Porsche cars from 1987 – 1994. It provides the home mechanic or Independent Porsche Specialist with a cost effective and invaluable tool to aid servicing and fault finding on Porsche cars.





Features & Functions

Note: The first production release of software is for the 928 range only. Further software updates for other Porsche models will be available when testing is finalised. DME code reading version for 944S/S2 and 968 are available.

Product Description

It is a small hand held unit. It is powered from the vehicle supply, so there are no internal batteries.

It has a 40 character 2 line alpha-numeric display. This enables operating instructions, menus and fault displays to be clearly shown without reference to written manuals. The display has a back light for operation in difficult environments.

The operation is intuitive and easy to use, with a single enter button for operation of all functions through scrolling options and on-screen prompts.

The Spanner - Porsche Diagnostic TesterIt is connected to the vehicle under test by a custom made lead. Two types of lead are available – one with the 12 pin rectangular connector used on 1987 and 1988 model cars, and another with the 19 way circular connector used on all other years.



The Spanner - Porsche Diagnostic Tester

An RS232 connection is also provided, enabling the use of a laptop computer for data viewing and control.





The RS232 port is also used for software updates.



Operational menus

When the unit is plugged into the car, the introductory screen display is shown. This is followed by a screen to select the type of car to be tested from the following options :

928; 944S; 944 TB; 964; 968

The display scrolls through these options in turn, and the required one is selected by the enter button.

Note: Not all versions of software offer all these types.



On pressing enter, the following options are shown in sequence (this example is for the 928, other cars are similar)

If LH/EZK/PSD ECU test is selected, then the operator will be requested to press the enter button to proceed. Then a request to switch on the ignition is shown, or if it has been left on in error, to turn it off and re-start the test.

The tester will then establish communication with the ECUs fitted to the car, these are LH/EZK or DME (combined Motronic fuel and ignition control) , PSD, Tiptronic (964 only) and Heater ECU (964 only).

If there any stored fault codes in the ECUs, they will be shown on the display with their fault code number, and also a text description - such as “O2 sensor over-rich mixture 1123” or “Knock sensor 1 faulty 2132".

The fault code number is the same as used in the fault finding section of the workshop manuals, which give detailed fault analysis routines.

After reading all the fault codes, the user is given the options of clearing the codes, or leaving them stored, and to proceed to the next ECU in sequence. When all the available ECUs fitted to the car have been read, then the tester displays “no further ECU responses” and returns the user to the top menu.


The airbag ECU is read in a different manner by the tester, so its diagnosis is selected from the top menu.

The second figure can either be a 1 or a 2. The former signifies that the fault is currently present, the latter that the fault is not always present (intermittent).

The third and fourth figures are the unique fault code identifier.

Examples: “Temperature sensor 2 Open circuit 1114” is a steady fault for the LH/DME ECU

“Knock sensor 2 (rear) Faulty 2232” is an intermittent EZK fault.

Actuator drive tests

This option allows the operator to check various actuators and switch inputs into the ECUs. This is to assist fault finding.

For example, the first check is of the fuel injectors. (Code 1311) The injectors are cycled on an off on a continuous basis until stopped by the operator. This enables checks to be made to determine if one injector is not operating, and if not then the actuating voltage feed can also be checked.

The second check is of the idle stabiliser actuator. . (Code 1321) The tester switches it repeatedly from one end of its range to the other. So electrical and vacuum checks can be carried out.


The third test is for the fuel tank venting valve to the carbon canister (where fitted) . (Code 1322)

The fourth check is for the resonance flap on the inlet manifold, so electrical and vacuum checks can be carried out. . (Code 1323)

The fifth check is of the engine speed pulse into the ECU from the engine flywheel sensor. . (Code 1331)

The sixth check is the throttle idle switch . (Code 1332)

The seventh check is for the wide open throttle switch (WOT switch) . (Code 1333)

The eighth and ninth checks are for the air conditioning switched input to the ECU . (Code 1334 and 1335)

The tenth check is the auto transmission Park/neutral switch to the ECU. (where fitted) . (Code 1336)

Airbag test

Note that this option is functional for MY 90 US and Canadian market cars only at present

Idle stabilisation adaptation

This allows a reset of the idle stabilisation loop. The engine is run for 45 seconds at idle speed, and the ECU adapts its default setting to the correct idle speed. This is routinely carried out by Porsche specialists when they have cars for serving or repair. Idle speed is properly set, and the car will generally run better generally, as the LH system is “adapted” to the engine. It is recommended that that is carried out at each annual service, and also if any work is done on the engine inlet system components.






Knock counting tests

This test monitors any engine detonations (“pinking” or “knocking”) from the engine, while being driven, over 10,000 cylinder firing cycles. Any detonation or pre-ignition as it is sometimes called can cause severe engine damage.

The tester monitors the knock count outputs from the ECU in the 10,000 period (approximately 2 minutes at 3,000 rpm). If the count is more than 50 knocks, then detonation is taking place and must be corrected.

During the test drive, the knock number display is continuously updated. At the end of the test period, the total number of counts is shown, and displays “Fault” if the total count is greater than 50.

The test can be repeated readily with a single “enter” press.



Digital dash diagnosis

This is a very useful (and little known) additional feature available to later cars with digital dashboards. Normally, a special link tool is required to enable this feature. The JDS Porsche tester has this function built in. It is fully described in the Porsche Service Information booklet WKD 495 021 of 1989. A copy of this is provided on the CD-ROM which is supplied with the tester.

Briefly, it can display:

If a fault has been signalled to the dash while driving, it will log the elapsed time or distance travelled after the warning. On some versions of digital dash, this feature of the tester can also be used to change the displayed language of the digital dashboard.

Comparison with KTS 300 “Hammer”

The KTS 300 communicates with the ECUs in a somewhat different manner. But the only major function not provided by the JDSPorsche tester is the bleeding of the PDS system fitted to the later 928s and the PDAS system fitted to the 964 Carrera 4 cars. Any stored PDS fault codes will be read out by the JDSPorsche tester (PDAS fault codes TBD)

JDSPorsche will be producing a separate control box to enable the bleed function to be carried out quickly and safely.

Note: The JDSPorsche tester will not diagnose the RDK system.

Availability and pricing

Production units are available now.

The first version will be for 928 cars only. Other cars will be added when testing is completed. An addition charge will be made for owners wishing to upgrade the software to include the other cars.

Customers in the USA can order from our agent 928 Specialists


Select “Browse by Parts Type” and then “Tools” . Alternatively, use the search box in the top right corner, and type “JDS” or “Spanner”.

Pricing: £360 GB, €550, $650 US delivered. The price includes the tester and a 19 way lead (12 way leads can be supplied) A CD-ROM with the User Instruction Manual, JDSPorsche Viewer installation software, Bootloader software and other useful information is also included.

A warranty of 2 years applies.

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