What exactly does it do? Do I need it now that my wires went to crap?

you know, I've been driving a sammy since 1990, and I've never figured out what the hell it does. Here's my educated guess: It tells the computer that your're in overdrive and it adjusts the air/fuel ratio accordingly. I don't know if that's right, but it sounds good.:smokin:

I believe on the carb model zuks, it tells the secondary to open.

The "fifth switch" is an input signal to the ECU. The ECU goes into closed loop mode (O2 sensor input used to control carburetor air bleed resulting in low emissions and good fuel mileage) when in fifth gear.


thanks to belleville95

okay that is what I thought is does. So....I am okay without it? At least till I track down another and want to change it. Thank you very much fellas

Where exactly do I locate this "fifth switch"?

the fifth switch basically controls the EGR Valve, not the close loop mode of the ECM or the secondaries...

Here, read this (it's from the FSM, so I am pretty sure I have the 'right' answer' :flipoff2: )

EXHAUST GAS RECIRCULATION (EGR) SYSTEM
This system controls the formation of NOx emission by recirculating the exhaust gas into the combustion chamber through the intake manifold.
The diaphragm mounted in the EGR modulator is operated by back pressure of the exhaust gas to open and close the valve. By this opening and closing action of the valve, the EGR modulator controls the vacuum transmitted to the EGR valve.

Under a low load condition such as low speed driving, the exhaust pressure is low. In this state, the diaphragm in the EGR modulator is pushed down by the spring force and the modulator valve opens to allow the air into the vacuum passage from the outside. As a result, the vacuum transmitted to the EGR valve becomes smaller and so does the opening of the EGR valve. Thus, less amount of exhaust gas is recirculated to the intake manifold.

Under a high load condition such as high speed driving, on the other hand, the exhaust pressure is high. By the high exhaust pressure, the diaphragm in the modulator is pushed up and closes its valve. As the air does not enter the vacuum passage in this state, the vacuum transmitted to the EGR valve grows larger and so does the opening of the EGR valve. Thus, larger amount of exhaust gas is recirculated to the intake manifold.

Under any one of the following conditions, the vacuum passage is closed by the TWSV or BVSV and the vacuum is not transmitted to the EGR valve which, therefore, doesn’t operate.


l When the coolant temperature is low. (BVSV is closed)
l When the gear shift lever is shifted to fifth gear position and fifth switch is turned on. (TWSV is closed)
l When HAC is turned on. (TWSV is closed)

Other than the above, EG R valve opens and closes in accordance with the EG R modulator operation.



The switch itself is on the driver side of the tranny. It is the switch that is the farthest back (the other switch is for the reverse lights).