Downstream Fuel Trim System 1 Lean
P2097-DOWNSTREAM FUEL TRIM SYSTEM 1 LEAN
For a complete wiring diagram refer to Diagrams/Electrical.
- When Monitored:
With the engine running in closed loop mode, the ambient/battery temperature above (-7° C) 20° F, altitude below 8500 ft.
- Set Condition:
If the PCM multiplies short term compensation by long term adaptive as well as a purge fuel multiplier and the result is below a certain value for 30 seconds over 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.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. ACTIVE DTC
NOTE: Check the vehicle repair history. If the 1/2 O2 has been replace make sure that the O2 sensor was properly installed and meets OEM specification.
NOTE: 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.
Is the DTC active at this time?
Yes
- Go To 2
No
- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
2. CHECKING THE EXHAUST SYSTEM FOR LEAKS
Perform the diagnostic procedure for *CHECKING THE EXHAUST SYSTEM FOR LEAKS. Checking the Exhaust System For Leaks
Were any problems found?
Yes
- Repair as necessary.
- Perform the Powertrain Verification Test . Powertrain Verification Test
No
- Go to 3
3. ENGINE MECHANICAL PROBLEM
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
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 1/2 O2 Sensor harness connector.
With the scan tool, monitor the 1/2 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 (K141) O2 Sensor 1/2 Signal circuit to the (K902) O2 Downstream Return 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.
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. (K141) O2 SENSOR 1/2 SIGNAL CIRCUIT
Remove the jump wire.
Ignition on, engine not running.
With the scan tool, monitor the 1/2 O2 Sensor voltage.
Is the voltage above 4.8 volts?
Yes
- Go To 6
No
- Check the (K141) O2 Sensor 1/2 Signal circuit for an 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. (K299) O2 SENSOR 1/2 HEATER CONTROL CIRCUIT
Turn the ignition off.
Measure the resistance between ground and the (K299) O2 Sensor 1/2 Heater Control circuit in the O2 Sensor harness connector.
Is the resistance below 5.0 ohms?
Yes
- Repair the short to ground in the (K299) O2 Sensor 1/2 Heater Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
No
- Go To 7
7. (K902) O2 DOWNSTREAM RETURN CIRCUIT
Measure the voltage on the (K902) O2 Downstream Return circuit in the O2 Sensor harness connector.
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 (K902) O2 Downstream Return 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