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Old 09-09-2011, 05:47 PM   #1
ptb
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Join Date: Sep 2011
Posts: 11
check engine light on

I have a 05 wrangler unlimited 2 door that i just bought and the check engine light was on. they replaced the 02 sensor, light came right back on. then they repaired a leak where the manifold meets the exhaust system. Drove 12 miles and check engine light's back on. It is throwing a P2098 code, which is basically the same thing they just fixed. Any thoughts on this?

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Old 09-09-2011, 09:13 PM   #2
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Location: Lakeland FL and Hooversville PA
Posts: 2,131
Well if it's not a jeep dealer working on it, I'd ask them to take it to one at their expense to have it properly repaired. Hopefully they did replace the correct sensor, there are 4 on yours. And the sensor and exhaust leak are only 2 of a slew of problems that can cause that code.

But in any case, here's the way to check for faults on the four sensor MIL's.



P2096-DOWN STREAM FUEL TRIM LEAN BANK 1
P2097-DOWN STREAM FUEL TRIM RICH BANK 1
P2098-DOWN STREAM FUEL TRIM LEAN BANK 2
P2099-DOWN STREAM FUEL TRIM RICH BANK 2
Test Note: All symptoms listed above are diagnosed using the same tests.
The title for the tests will be P2096-DOWN STREAM FUEL
TRIM LEAN BANK 1.
When Monitored and Set Condition:
P2096-DOWN STREAM FUEL TRIM LEAN BANK 1
When Monitored: With the engine running in closed loop mode, the ambient/battery
temperature above (-7C)20F, 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.
P2097-DOWN STREAM FUEL TRIM RICH BANK 1
When Monitored: With the engine running in closed loop mode, the ambient/battery
temperature above (-7C)20F and 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.
P2098-DOWN STREAM FUEL TRIM LEAN BANK 2
When Monitored: With the engine running in closed loop mode, the ambient/battery
temperature above (-7C)20F, 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.
P2099-DOWN STREAM FUEL TRIM RICH BANK 2
When Monitored: With the engine running in closed loop mode, the ambient/battery
temperature above (-7C)20F and 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.

GOOD TRIP EQUAL TO ZERO
EXHAUST LEAK
ENGINE MECHANICAL PROBLEM
O2 SENSOR
O2 SIGNAL CIRCUIT
O2 RETURN CIRCUIT
FUEL CONTAMINATION
TEST ACTION APPLICABILITY
1 NOTE: Check the [COLOR=green !important][COLOR=green !important]vehicle[/COLOR][/COLOR] repair history. If the O2 has been replace ensure
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 the DRBIIIt, read DTCs and record the related Freeze Frame data.
Is the Good Trip Counter displayed and equal to zero?

Yes ! Go To 2
No ! Refer to the INTERMITTENT CONDITION symptom in the
Driveability category.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
2 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.
Visually and Physically inspect the for holes, cracks and blockage in the exhaust
system.
Is the exhaust system is good condition?

Yes ! Go To 3
No ! Repair or Replace as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 5.

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
[COLOR=green !important][COLOR=green !important]TORQUE [COLOR=green !important]CONVERTER[/COLOR][/COLOR][/COLOR] 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 POWERTRAIN VERIFICATION TEST VER - 5.
No ! Go To 4
4 Ignition on, engine not running.
Disconnect the O2 Sensor harness connector.
With the DRBIIIt, monitor the O2 Sensor voltage.
The O2 Sensor voltage should read 5.0 volts on the DRBIIIt with the connector
disconnected.
Using a jumper wire, jump the O2 Signal circuit to the O2 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 POWERTRAIN VERIFICATION TEST VER - 5.
No ! Go To 5
5 Remove the jump wire.
Ignition on, engine not running.
With the DRBIIIt, monitor the O2 Sensor voltage.
Is the voltage above 4.8 volts?

Yes ! Go To 6
No ! Check the O2 Signal 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 [COLOR=green !important][COLOR=green !important]Powertrain [COLOR=green !important]Control[/COLOR][/COLOR][/COLOR]
Module in accordance with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
6 Measure the voltage on the O2 Return circuit in the O2 Sensor harness connector.
Is the voltage at 2.5 volts?

Yes ! Check the fuel system for contaminants.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
No ! Check the O2 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 in accordance with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER - 5



__________________
97 Sahara, 74 Renegade, 72 CJ5, 55 Willy's (the Beast) Boss 302, 6:34 gearing, Bose 901 speakers.
God I miss that Jeep. Forgot the kinda Jeep, 80 SX4.
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Old 09-09-2011, 09:38 PM   #3
ptb
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Join Date: Sep 2011
Posts: 11
thanks alot for the info shellby427. It is a jeep dealer that we are taking it to. The jeep only has 39000 miles on it and i can't imagine. it was taken only to the dealer for maintenance, so i am stumped. hopefully they will get it right when we take it in on monday or it's going back. thanks again for the info. ptb
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