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Throttle Position TP Sensors

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Throttle Position TP Sensors

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    2. 2

    3. What’s its purpose? Converts throttle valve angle into an electrical signal Provides PCM with information on: throttle opening rate of change 3

    4. Why? ‘electronic accelerator pump’ engine mode: idle part throttle wide open throttle (WOT) 4

    5. clear flood mode shift points wide open throttle (WOT): a/c operation and emission controls backs up other sensors 5 Why?

    6. potentiometer: electronic component which has a user-adjustable resistance a potentiometer converts mechanical movement into a variable voltage signal usually connected to PCM with a three wire harness 6 What is it?

    7. How does it work? terminal A= reference voltage from PCM terminal C= return path to ground terminal B= connects to a moveable wiper that sweeps across the resistor and returns a variable voltage signal 7

    8. 8

    9. THROTTLE POSITION SENSOR (TPS) CIRCUIT

    10. TPS WITH IDLE CONTACT SWITCH CIRCUIT

    11. TPS IN THE ETCS-i SYSTEM

    12. incorrect adjustment PCM may assume throttle is open and not control idle speed PCM may not see WOT and prohibit maximum engine output automatic transmission shift points erratic or intermittent signal can cause surge, sag or stall PCM + incorrect information = incorrect air/fuel ratio = increased emissions 12 What can happen?

    13. OBD 1 vehicles use 10/90 rule for monitoring sensor integrity signal voltage > 10% of reference = DTC signal voltage < 90% of reference = DTC OBD 2 vehicles use rationality strategy PCM “compares” information from other sensors to determine sensor integrity 13 On Board Diagnostics (OBD)

    14. DVOM testing: key on engine off backprobe connectors open throttle with accelerator pedal 14 Test twice, repair once

    15. 15 measure voltage between signal wire and ground at sensor signal should be low at idle slowly increase throttle opening signal should be high with throttle wide open

    16. How do we fix it? Always follow manufacturer’s procedures for testing sensors and diagnosing DTC’s 16

    17. Take a picture of it oscilloscope testing: a ‘visual’ voltmeter with a clock shows an image of the signal over a period of time 17

    18. 18 A dropout or glitch

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