How To Test a RB25 TPS Sensor

How To Test a RB25 TPS Sensor


Otherwise known as the Skyline throttle position sensor, the RB25 TPS Sensor is a multi-pin unit that’s mounted to your throttle body. Whether you are planning a RB25 engine swap, or you own a Skyline, problems with your TPS can cause serious issues. This guide can also help you calibrate your RB25 TPS Sensor when upgrading your Skyline throttle body.

Today I’ll be showing you how to test the RB25 TPS Sensor in a Nissan Skyline R33. Depending on which series of RB25 you own, you might have one connector or two connectors for your throttle body.

prostreet-r331This guide assumes that you still have the factory R33 throttle body, and you haven’t upgraded quite yet.

You will also notice that this guide is working from a top mount intake manifold or crossover intake manifold. If you’ve upgraded to a front facing intake manifold the location of your RB25 TPS Sensor will be different.

This guide can also help when you have imported a JDM RB25 engine and your throttle sensor is broken or seems to be failing. Some of the more common Nissan Skyline problems range from poor throttle response or even a bad idle.

If your RB25 TPS sensor uses two sets of three pin connectors, you might be confused. Although this guide is for the throttle sensor in your Skyline engine, I’ll show you how to test the throttle valve or idle switch. The RB25 idle switch is the set of three pin connector that’s mounted on the top of your throttle body.

test your RB25 TPS 4This is commonly a gray switch and one that’s easy to test. This three pin connector is what helps determine your RB25 engine speed or idle.

Testing your idle switch or throttle valve is easy to do using a digital multimeter. You’ll see the RB25 idle switch connector below, and you’ll need to turn the dial setting of your multimeter to read or measure resistance Ω.

RB25 idle switchBegin by measuring between pins 1 and 2 of your RB25 idle switch. Do this by unplugging your idle switch connector and measuring directly at the idle switch. With your Skyline or RB25 accelerator pedal not depressed, you should see 0Ω. With your accelerator pedal depressed fully, you should see ∞Ω. You can also manually deflect the throttle open using your hand and measuring with the other.

Still having problems with the RB25 idle or issues with the throttle valve? Check out the RB25 idle switch wiring diagram below.

RB25 idle switch wiring

If your idle switch internal resistance checks out, you’ll need to check continuity. Refer to the wiring diagram above to check the continuity from idle switch harness at PIN 1 and the RB25 ECU of PIN 22. The next wire to check is PIN 2 on the idle switch harness and PIN 32 on the ECCS RB25 engine computer.

Testing your RB25 TPS Sensor

When you are ready to use your multimeter to measure and test your throttle sensor, you can begin by unplugging the bottom connector. With the connector unplugged you will be testing for power and ground and finally the throttle signal.

test your RB25 TPS 1

This connector can be tested using the RB25 TPS sensor wiring diagram below.

The first wire you will be starting with is the power wire. To test this insert and turn your ignition key to the “ON” position.

Wire 1 that leads to PIN 1 on your RB25 throttle position sensor, is the power wire. This wire heads back to PIN 48 on your RB25 ECU. With the ignition turned to the ON position you should have a switched power signal here.

RB25 throttle position sensor 1

The next wire to check is PIN 3 which happens to be the ground wire. This wire heads back to PIN 30 on your RB25 ECCS ECU. If you have both power and ground circuits here, the RB25 TPS sensor should be working properly. Now measure the internal resistance of your throttle sensor by measuring terminals 2 and 3 with your TPS unplugged. Now push down on your throttle blade to fully open your RB25 TPS. You should read between 2kΩ to 10kΩ with the accelerator or throttle body fully open.

If you are still having problems, you’ll need to check the signal circuit of the throttle sensor. This is the middle wire, or PIN 2 on our RB25 TPS sensor wiring diagram. Reconnect the RB25 TPS sensor and measure the middle pin by piercing the wire with the red lead of you multimeter.

With your RB25 throttle body in the closed position, you should see between 4.5 and 5.2 volts of signal. Now push open the throttle body to the fully open position and you should see the voltage scale smoothly up to 4.1 to 4.6 volts of signal. Slowly close the throttle body, and you should see the RB25 TPS sensor signal sweep smoothly. You should not have any missing gaps or spikes in the voltage.

If your RB25 TPS sensor has any issues or does not respond accordingly to the specifications above, replace your throttle sensor. Have any questions about this guide? Leave us a comment below and let us know!