Without Speed Density Update

Chart - Code 22 Throttle Position Sensor (Signal Voltage Low):

Wiring Diagram for Throttle Position Sensor .:

CODE 22 THROTTLE POSITION SENSOR (TPS) (SIGNAL VOLTAGE LOW)


Circuit Description:
The throttle position sensor (TPS) provides a voltage signal that changes relative to the throttle blade. Signal voltage will vary from about .5 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: Numbers below refer to circled numbers on the diagnostic chart.
1. Code 22 will set if:
Engine running
TPS signal voltage is less than about .25 volt for 3 seconds.
2. Simulates Code 21: (High Voltage) If the ECM recognizes the high signal voltage the ECM and wiring are OK.
3. TPS check: The TPS has an auto zeroing feature. If the voltage reading is within the range of 0.35 to 0.70 volts, the ECM will use that value as closed throttle. If the voltage reading is out of the auto zero range on an existing or replacement TPS, the TPS should be adjusted.
4. This simulates a high signal voltage to check for an open in CKT 417.
5. CKTs 416 and 432 share a common 5 volts buffered reference signal. If either of these circuits is shorted to ground, Code 22 will set. To determine if the MAP sensor is causing the 22 problem disconnect it to see if Code 22 resets. Be sure TPS is connected and clear codes before testing.


Diagnostic Aids:

A "Scan" tool reads throttle position in volts. Voltage should increase at a steady rate as throttle is moved toward WOT. Also some "Scan" tools will read throttle angle 0% = closed throttle 100% = WOT. An open or short to ground in CKTs 416 or 417 will result in a Code 22. CKTs 416 and 417 are routed through a mini harness. CKT 416 is connected to terminal "D" at the gray connector, CKT 417 is connected to terminal "H" at the black connector. "Scan" TPS while depressing accelerator pedal with engine stopped and ignition "ON". Display should vary from below 500 mV (.5V) when throttle was closed, to over 4500 mV (4.5V) when throttle is held at wide open throttle position. Also some "Scan" tools will read throttle angle. 0% = closed throttle. 100% = open throttle. If Code 22 is set, check CKT 416 for faulty wiring or connections. Refer to "Intermittents" in "DIAGNOSIS BY SYMPTOM - NO TROUBLE CODE STORED".

***THIS PROCEDURE HAS BEEN ADDED FROM TSB# 886E3 DATED NOV. 1987

The ECM has the ability to auto-zero the TSP reference voltage. Auto-zeroing can be described as the ability of the ECM to determine a closed throttle position anytime TPS voltage is within a specific range. As long as the TPS is within that specific range, the system will function properly.
When checking TPS output at closed throttle, there are different specifications for different 2.8L V6 applications. "Scan" tools having the ability to also read the throttle valve angle should read 0% when the throttle valve is closed. Do not adjust the TPS if the voltage is within the specified range and throttle valve angle reads 0%
ACCEPTABLE CLOSED THROTTLE RANGE (VOLTS) = 0.35 - 0.7 Volts
ADJUSTMENT SPECIFICATION = 0.55 +/- 0.1 Volts