Code 21 and/or 22: Throttle Position Sensor (TPS)

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Alibi
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car:: 89 Lesabre T-type
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Code 21 and/or 22: Throttle Position Sensor (TPS)

Post by Alibi » Fri Apr 11, 2008 1:27 am

Introduction

The TPS (throttle Position sensor) .Used by the ECM to determine the amount of throttle demanded by the driver. should read .33-.46 volts at idle to near 5 volts at wide open throttle.

The Throttle Position Sensor (TPS) is a POTENTIOMETER connected to the throttle shaft on the throttle body. By monitoring the voltage on the signal line, the ECM calculates throttle position. As the throttle valve angle is change (accelerator pedal moved), the signal of the TPS also changes.
At a closed throttle position, the output of the TPS is low. As the throttle valve opens, the output increases so that, at wide-open throttle, the output voltage should be above 4 volts.

The ECM calculates fuel delivery based on throttle valve angle (driver demand). A broken or loose TPS may cause intermittent bursts of fuel from an injector, unstable idle, because the ECM thinks the throttle is moving.A problem in the TPS 5 volts reference or signal circuits should set either a code 21 or 22. A problem with the TPS ground will set code 15, 21 and 23. once a trouble code is set, the ECM will use an artificial default value for TPS and some vehicle performance will return. A high idle will result when either code 21 or code 22 is set.

Troubleshooting

Removal and Replacement


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Sources:

Authors: Alibi

Dates Modified: 4-10-08, 4-15-08
Last edited by Alibi on Tue Apr 15, 2008 9:06 am, edited 1 time in total.
-Eric
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-'89 BLT

steveX

Post by steveX » Sun Apr 13, 2008 8:20 pm

Information moved to main Wiki Article.

steveX

Re: Code 21 and/or 22: Throttle Position Sensor (TPS)

Post by steveX » Mon Apr 28, 2008 5:15 pm

CODE 21 Throttle position sensor (TPS) circuit (signal voltage high)

Circuit Description:The throttle position sensors (TPS) provide a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from about .4 at idle to about 5 volts at wide open throttle.
The TPS signal is one of the most important inputs used by the ECM for fuel control and for most of the ECM control outputs.

Test Description: Number(s) refer to circled number(s) on the diagnostic chart.
1. code 21 will set if:
* TPS voltage is greater than 4.9 volts at any time.
or
* Engine is running and air flow is less than 15 gm/sec
* TPS signal voltage is greater than 2.5 volts
* code 34 not present
* All conditions met for 5 seconds with closed throttle, ignition "ON," or at idle, voltage at "YD pin 13"(dark blue wire) should be .33-.46 volt.

2. when the TPS sensor is disconnected, the TPS voltage will go low and a code 22 will set. therefore, the ECM and wiring or OK.

3. Probing the black wire "YD pin 5" with a test light checks the sensor ground circuit. A faulty sensor ground circuit will cause a code 21.

NOTE: if a code 21 is set, the ECM will use a defaulted value for TPS of about .5 volt.

Diagnostic Aids: A "scan" tool read throttle position in volts. With closed throttle, ignition "ON" or at idle, voltage should be .33-.46 volts. If not, see "fuel metering system".
An open in circuit (black wire YD pin 11) will result in a code 15,21.
If circuit (bark blue wire YD pin 13) is open or grounded when the vehicle engine is started. a high idle may result. A "scan" tool may read the following with circuit dark blue wire open or grounded:

TPS = .04 volt or less
RPM > 1000 in park
Desired idle = 725
IAC counts > 40
SES light "ON," code 22 set
If the intermittent is repaired without cycling the key "OFF," the "Scan" may read the following:
TPS = .42 volt
RPM > 1500 in park
Desired idle = 725
IAC count > 55
SES light "OFF"

Check for:
* Poor connection or damaged harness inspect ECM harness connector for backed out terminal "YD pin 13", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

* Intermittent test if connection and harness check OK , monitor TPS voltage while moving related connectors and wiring harness. if the failure is induced, the display will change. this may help to isolate the location of the malfunction.

* TPS scaling Observe TPS voltage display while depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from closed throttle TPS voltage when throttle was closed to over (4.0 volt) 4000mv when throttle is held at wide open throttle position. Typically, accelerator pedal travel only yields 4.1 or 4.2 volts maximum, but full throttle rptation at the throttle body should be about 5.1 volts.




CODE 22 Throttle Position Sensor (TPS) circuit (signal voltage low)

Circuit Description:The throttle position sensors (TPS) provide a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from about .4 at idle to about 5 volts at wide open throttle.
The TPS signal is one of the most important inputs used by the ECM for fuel control and for most of the ECM control outputs.


Test Description:Number(s) refer to circled number(s) on the diagnostic chart.
1. code 22 will set if:
* The ignition key is "ON"
* TPS signal voltage is less than .1 volt for 4 seconds

2. Simulates code 21: (high voltage) If ECM recognizes the high signal voltage the ECM and wiring are OK.

3. With closed throttle, ignition "ON" or at idle, voltage at "YD pin 13" should be .33-.46 volt.

4. Simulates a high signal voltage. check circuit (dark blue wire or TAN wire) for an open.

Diagnostic Aids: A " scan" tool reads throttle position in volts. voltage should increase at a steady rate as throttle is moved toward WOT. an open or short to ground in circuit (gray wire) or ( dark blue wire) will result in a code 22.
If circuit ( dark blue wire) is open or grounded when the vechicle engine is started, a high idle may result. A "Scan" tool may read the following with circuit ( dark blue wire) open or grounded.

TPS = .04 volt or less
RPM > 1000 in park
Desired idle = 750
IAC counts > 40
SES light "ON," code 22 set.

If the intermittent is repaired without cycling the key "OFF," the "scan" may read the following.

TPS = .42 volt
RPM > 1500 in park
Desired idle = 725
IAC counts > 55
SES light "OFF"

Check for:

* poor connection or damaged harness Inspect ECM harness connector for backed out terminal "YD pin 13" ,proper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

* Intermittent test If connection and harness check OK, monitor TPS voltage display while moving related connectors and wiring harness. if the failure is induced, the display will change. this may help to isolate the location of the malfunction.

+ TPS scaling Observe TPS voltage display while depressing accelerator pedal with engine stopped and ignition "ON". Display should vary from close throttle TPS voltage when throttle was closed, to over 4.0 volts (4000mv) when throttle is held at wide open throttle position. typically, accelerator pedal travel only yield 4.1 or 4.2 volts maximum, but full throttle ratation at the throttle body should be about 1.5 volts.

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