TRW SPS (TYPE 1) - System Overview
At some point in mid 1996, this system replaced the bright Yellow and Red MPS1 system from TRW in all models. The only exception to this is in North American Specification Range Rover (P38) vehicles where it was retained until the 1999 revamp which introduced MPS2. It's main difference is that it uses a single internal crash sense, hence the designation change from MPS to SPS.
SM012 - TRW SPS (TYPE 1) - System Help file
Version 1.27

TRW SPS (TYPE 1) - Known Fitments
Vehicle makes, models and variants known or believed to be using this vehicle system, required diagnostic lead and degree of known compatibility.

Vehicle Make Vehicle Model Vehicle Variant Diagnostic Lead
Land Rover Range Rover MK II (P38) (non NAS) 1996-1999 Black OBDII Lead
Land Rover Discovery 1996 > Black OBDII Lead
Rover 800 1996 > Black OBDII Lead

TRW SPS (TYPE 1) - Physical Details

TRW SPS (TYPE 1) - Pin Outs
Details of the pin usage for the ECU connector(s).

1 - 4 Not Known
5 - 8 Not Used
9 Data Link Connector
10 - 11 Not Used
12 Instrument Cluster
13 Instrument Cluster
14 Ground
15 Engine Compartment Fusebox
16 - 30 Not Used

SM012 - TRW SPS (TYPE 1) - Diagnostic Capabilities (Read Fault Codes)
Each airbag system can self detect up to 24 faults. Most of these are major or safety related faults causing full system shutdown with only a few being minor caused by, for instance, a flat battery. The systems perform a self-diagnostic test that takes about 15 seconds whenever the ignition is switched on, logging any faults that are found, then at regular intervals thereafter. Resistors are placed at strategic points in the airbag wiring harness / loom giving the systems the ability to self detect open or short circuits. Main loom loops are from the ECU up the column through the spiral cassette through the airbag and back through the spiral cassette to the ECU; from the ECU through the passenger airbag and back again; on MPS systems, one through each of the two crash sensors mounted behind the head lamps at the front and then returning to the ECU, then two loops each going to the instrument cluster, through a bulb each and back again. In accordance with the manuals, no repairs must be carried out on the loom at all; hence, no wiring diagram is supplied in the manufacturer's manuals. All problems involving the airbags, spiral cassette, crash sensors, or loom must be done in strict accordance with the relevant manufacturer's workshop manual instructions. There is a deep memory within the airbag ECU that keeps a long-term record of resets to detected faults. This means that if a particular connection was poor and went open circuit - even just once - the fault would be logged by the system as "a sensor is open circuit" and the airbag warning light would come on. If the fault was not found and the fault code memory was cleared it would be very likely to reappear. This would be logged as an intermittent fault within the system.

SM012 - TRW SPS (TYPE 1) - Diagnostic Capabilities (Clear Fault Codes)
This function checks the fault code memory for resident faults and clears the fault code memory if the fault has been rectified. Having deleted the faults the system then rechecks the fault memory to ensure that it is clear. Failure to clear the fault memory successfully is usually due to the system re-logging the fault the moment the fault memory is clear, meaning that the fault has not been rectified properly and as far as the system is concerned, still exists. The system may also carry out a re-check for successful clearing of the fault code memory but then the system may re-log the fault shortly after.

SM012 - TRW SPS (TYPE 1) - Diagnostic Capabilities (Settings)
Values, configuration settings, and other stored information which can be read from the ECU, edited and then rewritten back. Read settings can also be stored as a standard HTML page for reference. These pages can then later be re loaded and re written back to the ECU. Please note that some values may be read only due to the fact that they are supplied from the ECUís ROM or are internally calculated.

  • System type: Some airbag ECU's / DCU's are fitted in different vehicle models. Where this is the case this value shows which system has been detected. Where the ECU / DCU type is unique to a vehicle model, this value then indicates the vehicle model.
  • Serial number: The electronically stored serial number for this airbag ECU, and can be found printed on a label affixed to the top or side of the ECU.