Hi does anyone have wiring info on SRS for disco 1 '97. I have no srs lights when I turn ignition on, Hawkeye cannot communicate with the control unit /ecu. I replaced control unit, the srs lamps are in Tacho which has been replaced (when I converted to MPH) a few times. After looking through Rave I found a reference to power to SRS controller on Power distribution schematic which shows F7 goes to pin 1 on controller and the wire in plug to controller is also labelled "1" but there is no power present at that end. I am hoping someone has info to save me ripping loom apart. Is it possible there is a fusible link internally to the loom as it states in the event of air bag deployment to replace all components including the loom.
sierrafery
Well-Known Member
Hi, you need the electrical troubleshooting manual: https://docdro.id/g1aV6zE, go to Circuit - Warning lamps diagrams untill page 100 to see how it is cos there's a separate lamp control unit in ithe IP(instrument pack), the SRS(airbag control unit) ECU is something else... then enter in Connector to see if the IP's C223 gets power from F7 , the SRS.airbag control unit is something else and if it has no power the warning lamp should be on to show that it doesnt work, if you get power to IP's C233 pin 1 then the problem is within the IP if no power you'll have to check the wiring from F7 or simply rewire it
Thanks I have that manual. I think the warning lamp circuit on the tacho is controlled by the main srs controller I think its the bottom wires that go down. I will try and remove speedo and air bags and meter it all.
sierrafery
Well-Known Member
It's not so simple, the warning lamp is switched on by the IP's controller and the SRS/airbag controll unit has to switch it off with power on the earth path when the system is in complete working order and when the system has a fault the airbag controll unit doesnt send power on the earth path and the lamp comes on . That's the way they work for all electronically controlled systems cos if any ECU fails for some reason the lamp must come on. For example if you unplug the SRS ECU(or any other ECU) or an ECU remains without power for a reason the lamp must come on cos it means that the system doesnt work if you see what i mean, the description is vague but the principle is like i say, believe me or not cos if it wasnt so how would you know if the SRS ECU remains without power while driving and you have no SRS at all?
SRS Indicators
The SRS Indicators are controlled by the Air Bag
Diagnostic Control Module (Z151) and the SRS
Indicator Control Circuit of the Instrument Cluster
(Z142) to indicate SRS System faults.
dont compare it with the oil pressure warning which is controlled by a simple switch cos that's the other way around and has no electronics, the lamp has power one side and gets earth from the N/C switch to come on then the oil pressure opens the switch and the lamp goes out... when any ECU is involved the lamp must come on if the ECU has no power cos you must have the warning that the system which is controlled by that particular ECU doesnt work then
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