From ilimzn@hotmail.com Mon Sep 9 07:48:08 2002 Date: Fri, 06 Sep 2002 16:13:35 -0000 From: ilimzn Reply-To: XM-L@yahoogroups.com To: XM-L@yahoogroups.com Subject: [XM-L] Re: How many ECUs? There can be up to 3 ECUs in the ECU box (behind the right headlight), even for an early diesel. 1) Hydractive (if the car is so equipped), black cover box with light back, two connectors, white and black. 2) ABS (Bendix), (if the car is so equipped), Al alloy box with one long connector that inserts 'on an angle' by hooking into a metal hook on one side, then pressing down. 3) Control or EGR ECU for engine. This depends on injection system and can be none, Bosch or Lucas. Mechanical systems without EGR (Can be Lucas/CAV or Bosch) do not have an ECU. EGR with Bosch pump has an ECU that looks kind of like a cross between the suspension and ABS one, has one connector larger than the ones on the suspension but smaller than the ABS, also uses a similar mating plug to the latter. It's purpose in life is to operate the EGR valve, and I think (but have never had a chance to test this) operate the glow plugs via an outboard relay. The engines equipped with this type of system look slightly different.. First, the inlet manifold is metal instead of the black plastic used on non-EGR. There is an EGR valve between that metal part and the exhaust on the lefthand side of the engine, looking inside the engine compartment the usual way. The valve is pneumatically operated via an electric vacuum pump, also operated via the ECU through an outboard relay. The injection pump is always Bosch, and the system has two extra sensors - one is a potentiometer on top of the pump power lever that tells the ECU about power demand. Another is an extra temperature sensor (usually with a red plastic housing). The ECU also uses the RPM sensor output. In later versions of this system, this ECU also drives the on-board computer, and provides fuel consumption figures, but as far as I know this only made it to the Xantia. The third possibility is a Lucas ECU (the one that has the RPM not operating problem), in which case this controls the injection pump, obvioulsy Lucas/CAV. I have never seen one of these in an XM myself, this type was never sold in Croatia. The XM is very popular there now, since it is a LOT of car for little money, so no doubt this type is also appearing, as nearly all XMs are used car imports. On gasoline cars, the engine control ECU (several possible types) takes the place of the EGR/engine ECU described above. Apart from this, there are a number of electronic boxes in the car. 1) Temperature control unit - located with the rest of the relays and fuses to the left of the steering wheel below the dashboard on LHD models. It controls the fan relays and the temperature gauage, as well as the yellow 'temp rising' warning light. It also feeds an 'engine hot' signal to the AC. 2) AC ECU (if the car is so equipped), is behind the ventilation/temperature controls in all cases. 3) Under the glove compartment: - Light test/control box (blue with two rows of connections) - Central locking (longish black box, also connects to receiver in the reading light base) - Interior light dimmer (smaller black or gray box) - Engine speed splitter (if car is equipped with cruise control, but also appears for some engine ECU configurations and board computer), splits the output of the vehicle speed sensor between board computer, suspension ECU and cruise control 4) In driver side door - electric windows 5) In the dashboard: - status display - clock/board computer - oil level sensor driver/controller - RPM signal conditioner and converter 6) In the engine compartment - Diesel preheat timer (on models that do not have an ECU, on models that do, it is replaced by a high power relay), bolted to the front of the battery holder. - Cruise control (various versions) And I'm sure I'm forgetting something... Z ------------------------ Yahoo! Groups Sponsor ---------------------~--> 4 DVDs Free +s&p Join Now http://us.click.yahoo.com/pt6YBB/NXiEAA/MVfIAA/6jLplB/TM ---------------------------------------------------------------------~-> Shortcut URL to this page: http://groups.yahoo.com/group/XM-L Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/