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For Info: 96+97 Exp = Bosh Immobiliser controls fuel pump

pmcmaster

Active Member
Joined
October 16, 2003
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City, State
Chelmsford (UK)
Year, Model & Trim Level
97 Estate
For anybody with a 96 or 97 Exp 4.0 fitted with a Bosh immobiliser (VIM). If you are having intermittant fuel pump problems and there is an electrical block fitted to the top of your fuel pump assembly (PSM=Pump Switching Module) (check the wiring harness at the block near to the rear of the fuel tank, you will have Red/Green and White/Lt Blue wires for this PSM). You may find (as I have to my cost) that the problem is the VIM NOT the fuel pump, see below.
96 & 97 Explorers of my model are fitted with a Bosh immobiliser, the PSM on top of the pump assembly is a data signal controlled pump cut out switch i.e. the power supply to the pump passes through this data signal controlled electronic switch, when you turn the ign on and the immobiliser has not been triggered the immobiliser sends a coded data signal to the pump switch which then allows current to pass through to the pump. In my case the immobiliser was sending an incorrect signal rather than no signal (which was why it hadnt triggered an error code).If the immobiliser is tripped (by breakin etc) the immobiliser then 'locks' the pump switch and can only be 'unlocked' by turning the ignition on and leaving on for 45minutes. Is it possible to design anything more complicated than this?. Under normal 'error' circumstances the immobiliser dash light will flash error codes (similar to the older OBD-I codes) i.e. flash pause flash pause flash flash flash = 113, this sequence is repeated twice then light stays on. Also if you replace the fuel pump assembly complete you will have to leave the ignition turned on for 45mins for the immobiliser to reset the PSM. Hope this is of some help. (the bad news is this Bosh Immobiliser has just cost me £530 ($950 i think))
 






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