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Re: If you're at base boost and you're cruise isn't working Posted by Bill Homer [Email]  (#3427) [Profile/Gallery]
(more from Bill Homer) on Thu, 5 May 2005 08:22:11
In Reply to: If you're at base boost and you're cruise isn't working, turrbo   [Profile/Gallery]
, Wed, 4 May 2005 17:46:08
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(the following applies to 1994 cars without TCS, don't know about cars with TCS)
Turrbo has the right idea, but I think is confusing the purposes of the cruise disengage switch(es) and the brake light switch.
1. On 1994 cars (and possibly different for other years), the pair of self-adjusting switches on the clutch and brake pedals will disable the cruise control when engaged. These are the switches with two leads only, not the larger three lead brake light switch, also attached to the brake pedal mechanism. When cruise is "ON", your car will be limited to base boost (so it doesn't take off like a rocket), when "OFF" it should have no effect on boost. These switches do not connect to the Engine Control Unit (ECU), only to the Cruise Control system.
2. Brake pedal switch will limit the ECU to base boost when the brake lights are on (don't need full boost when stopping, do you?). When brake pedal is depressed, a +12V signal is sent to pin 15 of the ECU, boost is limited to base boost.
3. There are additional sensors for the gear selector, limiting the ECU to base boost in P or N on automatic transmission cars, R on manual cars.
On activation of the Cruise Control system, pin 1 of the Cruise Control box will signal +12V (or close), this is connected to pin 36 of the ECU. A high voltage here will tell the ECU to limit boost to base boost (the factory trionic manual is actually wrong/reversed on this point!). On my car, pin 1 of the Cruise Control module was stuck on +12V whether the car was on or off, irregardless of whether cruise was engaged or not. A very simple way to eliminate the cruise contol from your search is to disconnect the module: pin 36 on the ECU will get internally pulled down to ground voltage.
I suggest that the first thing you do however is measure the resistance leads on the BPC solenoid, per my previous post - if necessary, get a cheap $10 multimeter anywhere, you don't need much accuracy here. The BPC is a high-failure item (and seriously overpriced).
posted by 136.182.2...
, Wed, 4 May 2005 17:46:08, Thu, 5 May 2005 08:22:11 <-- Viewing This Message
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