P2098
P2098-DOWNSTREAM FUEL TRIM SYSTEM 2 LEANP2098-Downstream Fuel Trim System 2 Lean:
WHEN MONITORED
With the engine running in closed loop mode, the ambient/battery temperature above (-7° C) 20° F, altitude below 8500 ft and fuel level greater than 15%.
SET CONDITION
If the PCM multiplies short term compensation by long term adaptive and a certain percentage is exceeded for two trips, a freeze frame is stored, the MIL illuminates and a trouble code is stored. Two Trip Fault. Three good trips to turn off the MIL.
POSSIBLE CAUSES
- Exhaust leak
- Engine mechanical
- 2/2 O2 sensor
- (K243) O2 2/2 signal circuit
- (K399) O2 heater 2/2 control circuit
- (K904) O2 return downstream circuit
- Fuel contamination
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. ACTIVE DTC
NOTE:
- Check the vehicle repair history. If the 2/2 O2 has been replaced make sure that the O2 sensor was properly installed and meets OEM specification.
- Check for contaminants that may have damaged the O2 Sensor: contaminated fuel, unapproved silicone, oil and coolant.
Ignition on, engine not running.
With a scan tool, read DTCs.
Q: Is the DTC active at this time?
YES: Go To 2
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Component Tests and General Diagnostics
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
2. EXHAUST LEAK
Turn the ignition off.
WARNING: TO AVOID PERSONAL INJURY FROM THE EXHAUST SYSTEM BEING HOT, ALLOW THE EXHAUST TO COOL DOWN TO A SAFE TEMPERATURE BEFORE PERFORMING A PHYSICAL INSPECTION. FAILURE TO FOLLOW THESE INSTRUCTIONS CAN RESULT IN PERSONAL INJURY OR DEATH.
Visually and Physically inspect the exhaust system for holes, cracks and blockage in the exhaust system.
Q: Is the exhaust system is good condition?
YES: Go To 3
NO: Repair or Replace as necessary. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
3. ENGINE MECHANICAL
Check for any of the following conditions/mechanical problems.
AIR INDUCTION SYSTEM - must be free from leaks
ENGINE VACUUM - must be at least 13 inches in neutral
ENGINE VALVE TIMING - must be within specifications
ENGINE COMPRESSION - must be within specifications
ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks ENGINE PCV SYSTEM - must flow freely
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - no internal vacuum leaks
FUEL - must be free of contamination
FUEL INJECTOR - plugged or restricted injector; control wire not connected to correct injector
Q: Are there any engine mechanical problems?
YES: Repair as necessary. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 4
4. O2 SENSOR
Ignition on, engine not running.
Disconnect the 2/2 O2 Sensor harness connector.
With the scan tool, monitor the 2/2 O2 Sensor voltage.
The O2 Sensor voltage should read 5.0 volts on the scan tool with the connector disconnected.
Using a jumper wire, jump the (K243) O2 Sensor 2/2 Signal circuit to the (K904) O2 Return Downstream circuit in the O2 Sensor harness connector.
NOTE: The voltage should drop from 5.0 volts to 2.5 volts with the jumper wire in place.
Q: Did the O2 Sensor volts change from 5.0 volts to 2.5 volts?
YES: Replace the O2 Sensor. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 5
5. (K243) O2 SENSOR 2/2 SIGNAL CIRCUIT
Remove the jump wire.
Ignition on, engine not running.
With the scan tool, monitor the O2 Sensor voltage.
Q: Is the voltage above 4.8 volts?
YES: Go To 6
NO: Check the (K243) O2 Sensor 2/2 Signal circuit for a open or short to voltage. Inspect the O2 Sensor connector and the PCM harness connector. If OK, replace and program the Powertrain Control Module. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
6. (K399) O2 SENSOR 2/2 HEATER CONTROL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the C3 PCM harness connector.
Measure the resistance between ground and the (K399) O2 Sensor 2/2 Heater Control circuit in the O2 Sensor harness connector.
Q: Is the resistance below 5.0 ohms?
YES: Repair the short to ground in the (K399) O2 Sensor 2/2 Heater Control circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 7
7. (K904) O2 RETURN DOWNSTREAM CIRCUIT
Measure the voltage on the (K904) O2 Return Downstream circuit in the O2 Sensor harness connector.
Q: Is the voltage at 2.5 volts?
YES: Check the fuel system for contaminants. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Check the (K904) O2 Return Downstream circuit for a short to ground, open, or short to voltage. Inspect the O2 Sensor connector and the PCM harness connector. If OK, replace and program the Powertrain Control Module. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test