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Cruise has little to do with the problem Posted by Bill Homer [Email]  (#3427) [Profile/Gallery]
(more from Bill Homer) on Wed, 16 Jul 2008 16:02:27
In Reply to: Re: ECU - BPC epair didn't seem to work, next step?, oldsaab, Tue, 15 Jul 2008 22:12:01 Members do not see ads below this line. - Help Keep This Site Online - Signup |
As I recall, your car is a 1994; my car is a 1994 as well. The cruise control function changed in 1995 cars, so the following is only applicable up to and including 1994.
The only connection between Cruise Control and the ECU is the red wire that indicates to the ECU that the cruise is ON and ENGAGED (two different steps, as the cruise light can be illuminated "ON" but the cruise function not currently engaged). The "cruise engaged" signal is transmitted to the ECU over this red wire; I recall that "engaged" is signalled by the Cruise Control pulling the +12 V signal down to ground - opposite of what is in the factory manual!
The small white plunger-type pedal switches above the brake and clutch pedals disengage the cruise function, but have no direct connection with the ECU and its boost function - recall that cruise control is an option in some markets and some cars can have full boost with no cruise control, which is an add-on feature.
In a previous round of discussion on your base boost problem, you said that you disconnected the cruise control box. Is it still disconnected? If so, good - it is out of the picture for diagnosing the base boost issue. Leave it disconnected for now, particularly if it does not work (a frequent problem with 1992 - 1994 cruise boxes).
Electrical signals that do signal the ECU to limit boost to base boost:
1. Brake pedal - the main brakelight switch, not the small switch that disengages the cruise control. Boost is limited to base boost when the brake pedal is applied.
2. Reverse - if the car is in reverse, boost will be limited to base boost.
3. Cruise - as described above.
As a wild card guess, is it possible that the issue is purely mechanical vs. electrical? A couple of the things to check are the E-clip or Cotter pin at the end of the Wastegate actuator, and the approximately 1 cm diameter tube that feeds in below the throttle body (these fall out over time, can be reattached with JB Weld).
I am particularly alarmed by the condition that you said the three transistors on the ECU board were in. Transistors typically do not fail by visibly melting. If they really are melted, you may have other issues with the ECU circuit board as collateral damage. Also, what did you use to solder the transistors in place? If you used a tool that is too large/hot, you can melt the foil traces on the printed circuit board, or easily cause a solder short between traces/pins. This is not the best place to learn how to solder.
posted by 63.87.52...
, Wed, 16 Jul 2008 16:02:27 <-- Viewing This Message, Thu, 17 Jul 2008 10:35:14, Fri, 18 Jul 2008 12:16:30, Thu, 17 Jul 2008 15:53:49, Thu, 17 Jul 2008 20:01:51, Thu, 17 Jul 2008 21:32:45, Fri, 18 Jul 2008 12:31:15
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