CODE 998 HARD FALT? IS THIS POINTING AT THE.

Diagnostic Trouble Code (DTC) 99/624 indicate a failure of EPC circuit.

DTC 625 indicates an opening in the driver circuit.

Possible causes:

Open or short in harnesses (internal/external).
Solenoid damaged electrically.
Key "OFF".
Disconnect transmission connector.
Key "ON", engine "OFF".
Measure the voltage between VPWR, EPC PWR circuit at transmission vehicle harness connector and chassis/battery ground.
Is voltage greater than 10.5 volts?

Yes -- Go to TC11. See: TC11 - Check Continuity of Solenoid Signal and VPWR Harness
No -- Service open in harness. Reconnect all components. Rerun quick test. See: Reading and Clearing Diagnostic Trouble Codes Reading Diagnostic Trouble Codes Quick Test Appendix (Detailed Testing Instructions)

Diagnostic Trouble Code (DTC) 335 indicates the Pressure Feedback EGR (PFE) / Differential Pressure Feedback EGR (DPFE) sensor is out of Self-Test range.

Possible causes are:

Damaged PFE/DPFE sensor.
Obstructed pressure inlet hose(s).
Garage exhaust ventilation system affecting PFE/DPFE sensor operation.

NOTE: PFE/DPFE system can sense a lack of pressure in the vehicle exhaust system. An efficient garage exhaust ventilation system that is installed during Key On Engine Off (KOEO) Test Mode may generate a DTC 335.

Remove garage forced ventilation system and properly vent to atmosphere.
Rerun KOEO Self-Test. See: Reading and Clearing Diagnostic Trouble Codes Reading Diagnostic Trouble Codes Quick Test Appendix (Detailed Testing Instructions)
Is DTC 335 present?

Yes -- Go to DL9. See: DL9 - Check PFE/DPFE Sensor Pressure Input Hose(s)
No -- ADDRESS other DTC's in KOEO Self-Test. If none. CONTINUE with remaining Quick Test. See: Reading and Clearing Diagnostic Trouble Codes Reading Diagnostic Trouble Codes Quick Test Appendix (Detailed Testing Instructions)

Continuous Memory Diagnostic Trouble Code (DTC) 157 indicates the Mass Air Flow (MAF) sensor signal went below 0.4 volt sometime during the last 80 warm-up cycles.

Possible causes:

Poor continuity in MAF sensor harness or connectors.
Intermittent open or short in MAF sensor or harness.
Damaged MAF sensor.
Idle Air Control (IAC) system failure (at closed throttle position).
Clear continuous memory. See: Reading and Clearing Diagnostic Trouble Codes Clearing Diagnostic Trouble Codes
Start engine and idle for 5 to 10 minutes.
Vehicle in "PARK" or "NEUTRAL".
Suddenly goose (greater than a half second) the throttle, approaching 1500 rpm.
Allow to return to idle.
Then, goose the throttle again, approaching 1500 rpm.
Key "ON", engine "OFF".
Run Self-Test to observe Continuous Memory DTCs.
Is Continuous Memory DTC 157 present?

Yes -- Go to DC13. See: DC13 - Air Leak at MAF Sensor
No -- Go to DC11. See: DC11 - Monitor MAF Circuit Under Simulated Road Shock