Throttle Position Sensor (Tps) [ Removal & Installation ]

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1988 Pontiac Grand Am 2.3L Eng SE 1Search™ TPS

THROTTLE POSITION SENSOR

Removal

Disconnect electrical connection from TPS. Remove TPS retaining screws. Remove TPS sensor.

Installation

1. With throttle valve in closed position, install TPS on throttle body. Ensure TPS lever engages with drive lever on throttle shaft. Install retaining screws and electrical connection.

2. On 2.0L and 2.8L (VIN 9) models, tighten screws. No adjustment is required. On all other models, adjust TPS to specification and tighten retaining screws. See THROTTLE POSITION SENSOR under ADJUSTMENTS in this article.

THROTTLE POSITION SENSOR (TPS) [ REMOVAL & INSTALLATION ]

Removal

Remove air cleaner and disconnect TPS electrical lead. Remove attaching screws, lock washers, retainers and TPS sensor. If necessary, remove screw holding TPS actuator lever to end of throttle shaft.

NOTE: On 4.3L engines, TPS is nonadjustable. After servicing, perform nonadjustable TPS output check. See appropriate article in TUNE-UP section.

Installation

1. With throttle valve in idle (closed) position, install TPS on throttle body. Ensure that TPS pick-up lever is located above TPS actuator lever. Install retainers, screws using thread locking compound (Loctite 262), and lock washers.

2. Connect electrical lead and install air cleaner. With ignition on, connect digital voltmeter to TPS "A" and "B" terminals, rotate TPS to obtain .45-.60 volt. Tighten attaching screws and recheck voltage.

THROTTLE POSITION SENSOR (TPS) CHECK/ADJUST

The Throttle Position Sensor is not adjustable. This ECM auto-zeros the TPS voltage at idle. This means the ECM reads the TPS voltage at idle as indicating 0% throttle opening (as long as the voltage is within the specified range). If the sensor is not within the specified range, circuit troubleshooting is necessary.

TPS BASE VOLTAGE SPECIFICATIONS (1)

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Application Voltage Throttle Position

Normal Range .45 - 1.25 Curb Idle

(1) ECM auto-zeros the TPS voltage at idle. This means the ECM reads the TPS voltage at idle as indicating 0% throttle opening (as long as the voltage is within the specified range).

Reassembly - Throttle Position Sensor (TPS)

Place throttle valve in normal closed idle position. Install TPS on throttle body with pick-up lever above throttle actuator lever. Install retainer, lock washers and 2 new attaching screws (coated with locking compound).

NOTE: Use care in removing injector to prevent damage to electrical connectors, fuel filter and nozzle. Injector is serviced only as unit.

CODE 21 - TPS SIGNAL VOLTAGE HIGH

The Throttle Position Sensor (TPS) provides a voltage signal that changes with the position of the throttle valve. Signal voltage will vary from about .5 volt at idle to about 5 volts at Wide Open Throttle (WOT).

NOTE: Test numbers refer to test numbers on diagnostic chart.

1. The following conditions must be met to set a Code 15:

1. Engine running at operating temperature.

2. No Codes 33 or 34.

3. MAP less than 65 kPa

4. TPS signal voltage greater than about 4 volts (78 percent).

5. Above conditions must exist for more than 5 seconds, or TPS voltage greater than 4.9 volts.

2. With TPS unplugged, voltage should reduce to a lower value, if ECM and wiring are okay.

3. Probing circuit No. 452 using a test light, checks TPS ground circuit. An open or very high resistance ground sets a Code 21.

Diagnostic Aids

When using a scan tool, throttle position should be displayed in voltage. Check TPS voltage with ignition on and engine off. At closed throttle display should read .49-59 volts. Voltage should increase at a steady rate as throttle is opened toward WOT position. Some scan tools will display in percentages such as:

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• 0 percent = closed throttle

• 100 percent = Wide Open Throttle (WOT)

An open circuit No. 452 will set a Code 21. Codes 15, 21 and 66 stored simultaneously could be result of an open circuit No.452. Check TPS connector for corrosion or improper connection. Check condition of connector seal, replace if necessary.

Fig 1: Code 21 Schematic - TPS Signal Voltage High

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Fig 2: Code 21 Flow Chart - TPS Signal Voltage High

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Fig 3: Code 21 Flow Chart - TPS Signal Voltage High

CODE 21, THROTTLE POSITION SENSOR SIGNAL VOLTAGE HIGH

The Throttle Position Sensor (TPS) provides a voltage signal that changes with the position of the throttle valve. Signal voltage will vary from one volt at idle to about 4.5 volts at wide open throttle.

Code 21 Will Set If:

• Engine is running and TPS voltage is greater than 2.5 volts for 5 seconds with engine speed less than 1300 RPM (auto. trans.) or 1400 RPM (man. trans.).

• MAP sensor detects high manifold vacuum (no load).

A Code 21 may also set if circuit No. 155 is open or circuit No. 417 is shorted to voltage.

NOTE: Test numbers refer to test numbers on diagnostic chart.

1. This step determines if Code 21 is a hard fault or an intermittent condition.

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2. This step simulates Code 22. If the ECM recognizes the low TPS voltage signal and sets Code 22, the ECM and circuits No. 416 and 417 are not at fault.

3. This step isolates a faulty sensor, ECM, or an open circuit No. 155.

Diagnostic Aids

A "Scan" tester displays throttle position in volts. Closed throttle voltage should be less than one volt. Voltage should increase gradually to about 4.5 volts, at a steady rate, as throttle angle is increased.

Fig 4: Code 21 - Schematic

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Fig 5: Code 21, Throttle Position Sensor Signal Voltage High

CODE 22 - TPS SIGNAL VOLTAGE LOW

The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to the position of the throttle valve. Signal voltage will vary from about .5 volt at idle to 5 volts at WOT.

NOTE: Test numbers refer to test numbers on diagnostic chart.

1. In order for Code 22 to set, engine must be running and TPS signal voltage should be less than about .2 volt for 3 seconds.

2. This test simulates high voltage (Code 21). If ECM recognizes high signal voltage, ECM and wiring are okay.

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3. TPS has an auto zeroing feature. If voltage is within range of .235-.75 volt, ECM will use that value as closed throttle. If voltage reading is out of zeroing range on existing or replacement TPS, TPS should be adjusted to .54-.56 volt.

4. A high voltage signal is simulated to check for an open in circuit No. 417.

5. Circuit No. 416 and No. 452 share a common sensor ground buffered reference signal. Code 22 will set if either circuits are shorted to ground. To determine if MAP sensor is setting Code 22, unplug connector and check for reset. Ensure that TPS is connected and clear codes before testing.

Diagnostic Aids

• 0 percent = closed throttle

• 100 percent = Wide Open Throttle (WOT)

Codes 22 and 66 stored simultaneously could be result of an open circuit No. 416. Check TPS connector for corrosion or improper connection. Check condition of connector seal, replace if necessary.

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Fig 6: Code 22 Schematic - TPS Signal Voltage Low

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Fig 7: Code 22 Flow Chart - TPS Signal Voltage Low

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Fig 8: Code 22 Flow Chart - TPS Signal Voltage Low

CODE 22, THROTTLE POSITION SENSOR SIGNAL VOLTAGE LOW

The Throttle Position Sensor (TPS) provides a voltage signal that changes relative to the position of the throttle valve. Signal voltage will vary from one volt at idle to about 4.5 volts at wide open throttle.

Code 22 will set if engine is running and TPS voltage is less than .2 volts for 5 seconds. A Code 22 may also set if circuits No. 416 or 417 are open or shorted to ground.

NOTE: Test numbers refer to test numbers on diagnostic chart.

1. This step determines if Code 22 is a hard fault or an intermittent condition.

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2. This step simulates Code 21. If the ECM recognizes the high voltage signal (greater than 4 volts) and sets Code 21, the ECM and wiring are not at fault.

3. This step checks for voltage from the TPS. The important thing is that the ECM recognizes the voltage as greater than 4 volts, indicating that circuit No. 417 and the ECM are not at fault.

Diagnostic Aids

Fig 9: Code 22 - Schematic

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Fig 10: Code 22, Throttle Position Sensor Signal Voltage Low

THROTTLE POSITION SENSOR (TPS) [ ADJUSTMENTS ]

NOTE: Throttle position sensor on 2.0L and 2.8L (VIN 9) are not adjustable.

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1. Install "Scan" tool and select TPS. With ignition switch in "ON" position, adjust TPS to specification. See TPS SPECIFICATIONS table. Adjust TPS output voltage in closed throttle position.

2. Tighten screws to specification. See TORQUE SPECIFICATIONS table. Recheck voltage readings.

TPS SPECIFICATIONS

Engine Application Code Output Voltage

2.3L VIN D .49-.59

2.8L VIN S .49-.61

2.8L VIN W .45-.61

3.0L VIN L .50-.59

3.8L VIN 3 .36-.44

3.8L VIN C .36-.44

5.0L VIN F .46-.62

5.7L VIN 8 .46-.62

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