Check engine light repeatedly turns on

Tiny
BXMT52
  • MEMBER
  • 2004 JEEP LIBERTY
  • 3.7L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 74,500 MILES
Check engine light keeps coming on several years now. I have had oxygen sensors replaced three times over the last six years. Now I am being told by one mechanic that it is the PCM the main computer which is going to be about of $1,000.00. Being told by another mechanic that it is the catalytic converter which will be about $700.00. He also wants to change the plug, s I just had all plugs changed at 55,000 miles I am now at 74000 miles. Does anyone have any suggestions what I should do? Very much appreciate anyone's thoughts thank you!
Saturday, December 1st, 2018 AT 5:14 PM

12 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good evening,

We need the code numbers to help you.

https://www.2carpros.com/articles/check-engine-light-top-ten-reasons

Do you know the code numbers?

Roy
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Saturday, December 1st, 2018 AT 6:22 PM
Tiny
BXMT52
  • MEMBER
  • 7 POSTS
In 2012, P0135 replaced 1 of 1 02 sensor. In 2015 P0138 replaced both lh upstream and downstream 02 sensors in 2018, P0132 replaced 1 of 1 02 sensor. Check engine light will not clear now.
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Saturday, December 1st, 2018 AT 7:02 PM
Tiny
ASEMASTER6371
  • MECHANIC
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What is the current code?

All the possibilities need to be checked. Codes rarely identify bad parts just failed systems.

Roy

135

P0135
Descriptor
O2 Sensor 1/1 Heater Performance
Probable Causes
Oxygen Sensor (O2S) Heater Control Circuit Open
Oxygen Sensor (O2S) Heater Element
Oxygen Sensor (O2S) Heater Ground Circuit Open
Oxygen Sensor (O2S) Heater Operation
Powertrain Control Module (PCM)

138

P0138
Descriptor
O2 Sensor 1/2 Circuit High Voltage
Probable Causes
Oxygen (O2) Sensor
Oxygen Sensor (O2S) Return Circuit Open
Oxygen Sensor (O2S) Return Circuit Shorted to Voltage
Oxygen Sensor (O2S) Signal Circuit Open
Oxygen Sensor (O2S) Signal Circuit Shorted to Voltage
Oxygen Sensor (O2S) Voltage Above 3.7 Volts
Powertrain Control Module (PCM)

132

P0132
Descriptor
O2 Sensor 1/1 Circuit High Voltage
Probable Causes
Oxygen (O2) Sensor
Oxygen Sensor (O2S) Return Circuit Open
Oxygen Sensor (O2S) Return Circuit Shorted to Voltage
Oxygen Sensor (O2S) Signal Circuit Open
Oxygen Sensor (O2S) Signal Circuit Shorted to Voltage
Oxygen Sensor (O2S) Voltage Above 3.7 Volts
Powertrain Control Module (PCM)
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Saturday, December 1st, 2018 AT 7:17 PM
Tiny
BXMT52
  • MEMBER
  • 7 POSTS
I am not sure what the current code is now. I just know it wont pass emissions test. I will have to find out. Looks like you are leaning towards a new PCM? What do you think about the catalytic converter? It seems to have lost its get up and go especially when trying to go up a hill.
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Saturday, December 1st, 2018 AT 8:18 PM
Tiny
BXMT52
  • MEMBER
  • 7 POSTS
The emissions failed due to oxygen sensor reject.
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Saturday, December 1st, 2018 AT 8:19 PM
Tiny
ASEMASTER6371
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No, I am more leaning to a wire harness issue.

Send me the current code so I can help you further.

Roy
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Saturday, December 1st, 2018 AT 8:20 PM
Tiny
BXMT52
  • MEMBER
  • 7 POSTS
Oh really? Okay, I will do that. Thank you so much for your help. Have a good night!
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Saturday, December 1st, 2018 AT 9:53 PM
Tiny
ASEMASTER6371
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You as well.

Roy
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Sunday, December 2nd, 2018 AT 4:18 AM
Tiny
BXMT52
  • MEMBER
  • 7 POSTS
Hi. Sorry it took so long to get you the code. Here is what it is showing now: p0135 02 sensor, heater bank 1 sensor 1. P0300 random misfire detected.
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Thursday, December 6th, 2018 AT 9:51 AM
Tiny
ASEMASTER6371
  • MECHANIC
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Okay, got it.

The 135 possibilities are below. This looks like a harness issue. I will attach a wire diagram for you to view as well.

P0135
Descriptor
O2 Sensor 1/1 Heater Performance
Probable Causes
Oxygen Sensor (O2S) Heater Control Circuit Open
Oxygen Sensor (O2S) Heater Element
Oxygen Sensor (O2S) Heater Ground Circuit Open
Oxygen Sensor (O2S) Heater Operation
Powertrain Control Module (PCM)

The 300 is below as well. The most common issue for this code is low fuel pressure from the fuel pump. That is the first thing I would check.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

300

P0300
Descriptor
Multiple Cylinder Misfire
Probable Causes
Automatic Shut Down (ASD) Relay Ouput Circuit
Coil Control Circuit
Engine Mechanical Problem
Fuel Injector
Fuel Leaks Down
Fuel Pressure
Fuel Pump
Fuel Pump Strainer
Fuel Supply Line Restricted
Ignition Coil
Injector Control Circuit
Intermittent Misfire
Powertrain Control Module (PCM)
Spark Plug

All these possibilities need to be checked.

Roy
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Thursday, December 6th, 2018 AT 10:27 AM
Tiny
BXMT52
  • MEMBER
  • 7 POSTS
Oh no. Sounds like lots to look at! Thank you for your help!
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Thursday, December 6th, 2018 AT 1:05 PM
Tiny
ASEMASTER6371
  • MECHANIC
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You are welcome.

Always glad to help.

Roy
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Thursday, December 6th, 2018 AT 1:11 PM

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