ECM CODE EO22 - OPEN TPS CIRCUIT
TEST CONDITIONS: Engine RPM is greater than or equal to 600.
FAILURE CONDITIONS: TPS value is less than -5 degrees (TPS parameter reads -10 to -6 degrees) for 1.5 seconds.
ACTION: ECM turns on "ENGINE CONTROL SYSTEM" light. ECM commands BCM to display "SERVICE SOON" message on CCDIC panel. ECM uses 12 degrees for TPS value with ISC throttle switch wide open, and 6 degrees for TPS value when ISC throttle switch closes. ECM stops using TPS to control ISC motor (it uses RPM for all ISC calculations).
The TPS is a 3-wire sensor receiving a 5-volt reference input from ECM over circuit No. 474, and a reference ground from ECM over circuit No. 476. The TPS sensor sends a sensor output signal over circuit No. 417 to the ECM.
The sensor output signal is a DC voltage that varies with throttle angle, the TPS signal voltage is low (about .5 volts at minimum air setting). At high throttle angles, the TPS signal voltage is high (about 4.5 volts at wide open throttle).
Code EO22 is set when the ECM sees a that throttle angle is out of limits (low TPS voltage) with engine running at idle or faster. Code is designed to detect a TPS signal, over circuit No. 417, open to ECM pin "D7".
Note. Test numbers refer to test numbers on diagnostic chart.
- Jumper 5 volts to TPS signal to see if ECM parameter will respond to high signal voltage on TPS inputs (circuit No. 417).
- Checks for an open/shorted TPS reference circuit.
- Checks for a grounded TPS signal (circuit No. 417).
- Fault is most likely at ECM connector or ECM. See CHART C1 - ECM REPLACEMENT CHECK before replacing ECM.
If code EO22 is intermittent, manipulate related wiring while observing ECM parameter ED01. Cycle TPS through its travel and tap on TPS with a pencil to test for intermittent TPS operation. If fault is induced, parameter will skip to -6 degrees or less. If wiring and connectors are okay, substitute a known good TPS sensor and retest.
Review snapshot data parameters stored with this code to verify failure. If failure is verified, check and repair intermittent wiring connection or sensor.
Flow Chart, Code EO22, Open TPS Circuit. Scheme 227
Note. If a hard code EO22 is accompanied by hard code EO32, see DFI Chart A, "Multiple ECM Codes Stored Hard".
Code EO22, Open TPS Circuit. Scheme 228
Ignition on. Engine speed greater than or equal to 304 RPM.
EST pulses are seen by the ECM before by-pass circuit is turned on (5 volts) or EST signal remains grounded after the by-pass circuit is turned on (5 volts).
ECM turns on "ENGINE CONTROL SYSTEM" light. ECM commands BCM to display "SERVICE SOON" message on CCDIC. If ECM sees 5-volt EST pulses with by-pass voltage at zero, caused by EST circuit open or by-pass circuit shorted to voltage, the ECM will not enable spark timing. The engine will start and run on base timing. If EST circuit is shorted to ground, the vehicle will start and stall when engine reaches 300 RPM (as by-pass turns on). When restarted, the ECM will not try to turn by-pass on, code EO23 will set, and engine will start and run on base timing.
The EST distributor produces one 5-volt reference pulse each time that a cylinder reaches 10° BTDC (base timing). These reference pulses are sent from distributor to the ECM over circuit No. 430.
The ECM adds spark timing information to the reference pulses received from the HEI module and sends out a 5-volt electronic spark timing pulses over circuit No. 423.
The ECM can choose to control spark timing. The HEI by-pass circuit is turned on by the ECM when the ECM wishes to control timing. When timing control is desired, the HEI by-pass circuit is turned off and the HEI module ground circuit No, 423. The ECM always sends EST pulses to the HEI, the HEI module shorts EST pulses to ground when the by-pass signal from the ECM to module is low (less than .5 volts).
Note. Test numbers refer to test numbers on diagnostic chart.
- Four 12" jumper wires must be obtained for use in diagnostic procedure. Jumper wires MUST have male and female Weatherpack Connectors (12014836 and 12014837) on either end. With distributor connector unplugged, use jumper wires to reconnect terminals. Use instructions provided in chart.
- With only distributor reference and distributor reference ground jumpered, engine will run on back-up spark control. This step checks for proper ground connection between ECM and engine, and between ECM and HEI.
- This step ensures that ECM is providing an EST output signal over circuit No. 423.
- This step checks the ability of the HEI module to ground EST signal with an open by-pass circuit.
