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Ron
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23001
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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I have a 2003 Ford Ranger, 4 Liter V6 with a manual 5 speed

Customer Question

I have a 2003 Ford Ranger, 4 Liter V6 with a manual 5 speed trans. it wont pass Connecticut emissions testing.
Reading the OBDII there are no trouble codes, however the testing site as well as my little OBDII reader say the Heated O2 sensors and the Cat sensors are "not ready".
I replaced the coolant temp sensor, same thing. Repair place said engine wasn't running hot enough, so I replaced the thermostat to the OEM recommended temp 195 degree.
Engine runs great still has the same three things wrong three sensors not ready.
Whats neXT, where do I look now??
Submitted: 4 months ago.
Category: Ford
Expert:  Chad Farhat replied 4 months ago.

Hi, I'm Chad ,Welcome To JustAnswer, I'm reviewing your question and I will be be posting a replay ASAP

Expert:  Chad Farhat replied 4 months ago.

you have oxygen sensor monitor not ready, why are we changing coolant sensor ?

how many miles on vehicle ?

do you have a scanner than can read o2 sensor live data?

Please let me know

Thank You

Chad Farhat

ASE Certfied Technician

Customer: replied 4 months ago.
162,300 miles, 02 sensors are 1 yr old. The scanner i have is the basic scanner.it will not read live data.
I changed the sensor because i was told that the monitors wont set untill the computer knows the engine is up to temp.
Expert:  Chad Farhat replied 4 months ago.

not true

Expert:  Chad Farhat replied 4 months ago.

if the o2 sensor heater circuit or o2 sensor bad itself it will not finish the monitors for it ,who told you that ?

Expert:  Chad Farhat replied 4 months ago.

possible causes

1- you have bad o2 sensor ( 4 on your jeep 2 upstream and 2 downstream )

2- catalytic converter clogged

3- wiring to o2 sensor damaged

4- PCM ( computer itself )

Expert:  Chad Farhat replied 4 months ago.

if the ect ( coolant temp sensor is bad ) it will cause it to run on open loop not closed loop

but it will finish the monitors but show a fault .

since you replaced ect sensor already, so we can take that out of the loop.

o2 sensors needs checked on a scanner ,if they r fluctuating from 0.1 to 0.9 volts

Customer: replied 4 months ago.
I don't have a jeep, I have only two 02 sensors. Wouldn't a clogged cat cause other problems with power and acceleration? this truck runs great even at high speeds,. How can I check the 02 sensors before replacing them?
Expert:  Chad Farhat replied 4 months ago.

if no scanner available , you can take them out and do a ohm test and compare with a known good one

Expert:  Chad Farhat replied 4 months ago.

sorry ford ranger and yes 2 sensors, i got mixed up with another post i m working on he has a jeep :)

sorry about that

Customer: replied 4 months ago.
Ok , thanks ill check / replace them this weekend and get back to you.
Expert:  Chad Farhat replied 4 months ago.

if the clogged cat is only partially clogged , you will have full power , but will not finish the monitors .

usually you will feel slight vibration in steering at idle .

Expert:  Chad Farhat replied 4 months ago.

ok sounds good

I m online daily from 10 am till 12 pm

Please let me know

Thank You

Chad Farhat

ASE Certified Technician