Need Help?

1998 Jeep Grand Cherokee Laredo 4dr

1998 Jeep Grand Cherokee
Trim Info:
Rear Wheel Drive, 4 Door, 2WD Special Purpose Vehicles
16 mpg city / 21 mpg hwy
Other Trims
Do you own this car?
Estimated Mileage
 Miles
Enter current mileage for most
accurate info about this vehicle


Track Your Service Records
Get Recall Alerts
Get Updated Value Estimates on Your Car.

back to question list

Ask the Community

Ask Our Auto Mechanics


January 6, 2013, 4:17 pm

Amber M
 

Question: Can a bad coolant temperature sensor cause a po420 code?

I have a 98 Jeep Grand Cherokee, and the Check Engine light came on today. I took it the the Advance for one of the code test. They just told me it was a po420 so i would need a new catalytic converter.
After doing research of my own I found that a bad coolant temperature sensor can also cause that code.

Since my coolant temperature sensor is bad would that be the reason for the po420 code? Or do i really need a new catalytic converter?


January 12, 2013, 9:20 am

Ron W
Expert Mechanic


Here is a link to information about that code.

P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

http://www.obd-codes.com/p0420

If the temp sensor is bad, the vehicle may not be running at operating temp when the OBD Cat and O2 sensors monitors run so an incorrect code could be set.

It is not very likely, and your cat is probably dead, but since you need a sensor anyway, change the sensor, clear the codes and see if the code resets. If it does, the cat is the most likely failure. If it doesn't, you just saved $500.


0/0 users found this helpful.

Ask our panel of certified auto mechanics a question. We pay for their advice so you don't have to



My Auto Score

See the free AutoCheck score

Meet The Experts
Kim Perrin
Kim Perrin is our resident mechanic here at DriverSide. Kim worked as…
Tyler Orr
Tyler Orr is an expert in German and Japanese cars and has been a mechanic …
Elizabeth Kriesten
Elizabeth Kriesten worked as an automotive technician for several years at Dodge…
Tips on Servicing

Car Brakes: How Do You Know When to Change Them?

By Zach Bowman For those who suffer a daily commute through heavy traffic, your vehicle's braking system can bring thousands of pounds of metal, plastic and empty Starbucks cups to a stop hundreds of times before you get to work. It goes without saying that these pieces wear out, but they do so slowly, meaning you may not notice they need attention until ...

Read more…