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Re: Another (different) up shift light question Posted by Justin VanAbrahams [Email] ![]() ![]() In Reply to: Another (different) up shift light question, MichaelG, Wed, 21 Feb 2001 23:11:44 Members do not see ads below this line. - Help Keep This Site Online - Signup |
First question is whether your car uses LH 2.4 or not. If it does, then you've got nothing really to check, all the computing is done by the ECU, and if it ain't working, there is something wrong with the ECU, or the connection between the ECU and the light.
If it does not have LH 2.4, there are only a few possibilities. There is a switch on the 5th gear cover on the tranny which can fail. If there is not continuity across it in gears 1-4, then that's your problem. There is a vacuum switch on the fender wall connected to the intake manifold (not the cruise control!) which can fail. You should be able to "induce" continuity across its connectors by either blowing or sucking on it - I don't remember which. If you can't get continuity, that's your problem. You've tested the thermo sensor - there should be continuity when it gets above 95 degrees F. Another component is the RPM signal - it won't work without an RPM signal (so it knows the car is running...), but if the car runs then the supplier of the signal is probably working... :) Depending on your car and its year, there may be a switch on the throttle butterfly which shorts to ground under normal circumstances, but will open when the throttle is at rest. Check that switch if you've got it (don't get it confused with the A/C cutout switch!) There should also be continuity between this switch and the US pin on the relay. Check to be sure the TPS is working and adjusted correctly. There's a relay in the main fuse panel, and that's it - that's all to the system. Obviously, check to make sure the relay has a good ground at pin 31...
There ain't that much to it. Don't rule out something stupid, like a bad ground or a bad contact at the bulb.
Good luck...
-Justin
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