TPS Idle Switch Multimeter Test (1993-1997 1.8L Toyota Corolla)

The 4-wire throttle position sensor on the 1993-1997 1.8L (7A-FE) Toyota Camry has an idle switch part and a TPS part. In this tutorial, I'm gonna show you how to test the idle switch part of the throttle position sensor.

If the TP sensor is replaced or loosened, it needs to be calibrated in a specific way. I'll also show you how to do that.

APPLIES TO: This tutorial applies to the following vehicles:

• 1.8L (7A-FE) Toyota Corolla: 1993, 1994, 1995, 1996, 1997.
• 1.8L Geo Prizm: 1993, 1994, 1995, 1996, 1997.

Throttle Position Sensor Test: If you need to test the throttle position sensor part of the idle switch, this tutorial will help:

• How To Test The Throttle Position Sensor (1989-1997 1.8L Toyota Corolla).

Where To Buy Your TP Sensor And Save

Need to buy a TP sensor for your 1.8L Toyota Corolla? You can grab one from your local auto parts store, but it's gonna cost you a lot more. Check out the prices at the links below and compare:

Not sure if the above TP sensor fits your particular 1.8L Toyota? Don't worry, once you get to the site, they'll make sure it fits by asking you the particulars of your vehicle. If it doesn't fit, they'll find you the right one.

Idle Switch Continuity Tests

To check if the idle switch is working properly, we're gonna measure continuity between two specific pins using a multimeter set to Ohms mode.

The TPS terminals you need to find are terminal #2 and terminal #1 (see the illustration above).

IMPORTANT: The throttle body includes a Throttle Opener Diaphragm Assembly. To test the idle switch, you'll need to apply vacuum to the Throttle Opener using a vacuum pump (for its exact location, check here: Location Of The Throttle Opener Vacuum Diaphragm).

1. Turn off the ignition switch and unplug the TPS from the engine wiring harness connector.

2. Place a feeler gauge of the specified thickness between the throttle stop screw and throttle lever. Then, check for the correct continuity using the table below (to see exactly where to insert the feeler gauge, check here: Location Of The Throttle Stop Screw). If the readings aren't within spec, adjust or replace the TPS assembly.

Idle Switch Continuity Specifications
Feeler Gauge Thick.	Pins	Ohms
0.016 In. (.40 mm)	1 and 2	Continuity
0.035 In. (.90 mm)	1 and 2	No Continuity

If the throttle switch on your 1.8L Toyota Corolla (or 1.8L Geo Prizm) fails any of the continuity tests above, don't rush to replace it just yet. First, check if it's simply misadjusted. The next section will guide you through the adjustment process.

Adjusting The Throttle Position Sensor Assembly

If you're replacing the throttle position sensor assembly, you've gotta adjust it to the correct spec before tightening it down.

Luckily, this adjustment is pretty straightforward, and I'll walk you through it step by step.

IMPORTANT: You need to apply vacuum to the Throttle Opener Assembly using a vacuum pump while adjusting the TPS.

NOTE: The Toyota repair manual recommends removing the throttle body from the intake manifold to make these adjustments. However, I’ve been able to adjust it without removing it —though it’s a bit more difficult than when I have removed the throttle body. If you find it too difficult to adjust the TPS with the throttle body in place, go ahead and remove it. Just be sure to use a new throttle body gasket and install it dry (without sealants).

Here's what you need to do:

1. Turn the ignition switch to OFF and disconnect the TP sensor assembly from its connector.
2. Apply vacuum (with a vacuum pump) to the Throttle Opener Diaphragm Assembly.
3. Set your multimeter to Ohms mode.
4. Insert a 0.035 in. (0.90 mm) feeler gauge between the throttle stop screw and throttle lever, then:
   • Check for continuity between terminals #1 and #2. Your multimeter should show NO CONTINUITY.
   • If there is continuity, slightly rotate the TPS until NO CONTINUITY is detected.
   • Lightly tighten the TPS screws.
5. Now, insert a 0.016 in. (0.40 mm) feeler gauge between the throttle stop screw and throttle lever, then:
   • Check for continuity between terminals #1 and #2. Your multimeter should show continuity.
   • If there's no continuity, rotate the TPS slightly until continuity is detected.
   • Lightly tighten the TPS screws.
6. Repeat steps 3 and 4 to confirm NO CONTINUITY and CONTINUITY exist at the correct feeler gauge thickness.
7. Once the TPS is properly adjusted, tighten the mounting bolts securely.
8. After tightening, recheck the continuity readings to make sure the TPS didn't shift while securing the bolts.

Location Of The Throttle Opener Vacuum Diaphragm

NOTE: The Throttle Opener Diaphragm Assembly is located on the throttle body assembly, right below the throttle plate linkage. The arrow (in the image above) points to it.

A vacuum hose connects to the Throttle Opener Assembly's vacuum inlet port. To perform the test, disconnect the vacuum hose from the inlet port and hook up your vacuum pump instead.

Location Of The Throttle Stop Screw

NOTE: To inspect or adjust the TPS assembly, you'll need to insert a feeler gauge between the throttle stop screw and the throttle lever.

The arrow points to the spot between the throttle stop screw and the throttle lever where you need to place the feeler gauge between them.

More 1.8L Toyota Corolla Tutorials

There are several more 'how to' tutorials that I've written that are 1.8L Toyota Corolla specific, that may be of further help. You can find them here:

• 1.8L Toyota Corolla Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test Engine Compression (1993-2008 1.8L Toyota Corolla).
• How To Test For A Blown Head Gasket (1993-2008 1.8L Toyota Corolla).
• Misfire Codes: How To Troubleshoot And Repair Them (1996-2008 1.8L Toyota Corolla).
• How To Test The Fuel Injectors (1993-1997 1.8L Toyota Corolla).