Q: My 4-cylinder S10 1999 failed on Cadillac converter slightly too warm not red.. it passed everything else.. no check engine light

asked by on

I failed smog test for the first time Cadillac converter slightly warmer but not red.. Temp 944... no check engine light is on... he said everything else looks good.?? Cadillac converter is 2 years old with warranty.. could an oxygen sensor be bad and not show check engine light.. .?????? My truck runs great

My car has 12557 miles.
My car has a manual transmission.

"Bad" is a relative term when it comes to oxygen sensors. It is possible for the oxygen sensor to slowly degrade and lose effectiveness over time but not so much so that the check engine light comes on. However, oxygen sensors can be tested using even inexpensive (DIY) scan tools such as the Bosch OBDII 1200 (or higher). You can graph the output of the sensor and also view the switching voltage range to see if it is functioning properly. What you want to do, with that or a similar scan tool, is also look at the fuel trims. If fuel trims are out of range, that’s a sign of poor engine running condition and will adversely affect emissions. Catalytic converter effectiveness is monitored by the downstream oxygen sensor and, as well, you can simply measure the in and out temperatures of the converter to see if it is actually working. The outlet temperature should be higher than the inlet. If your vehicle burns oil, that is something to consider both in terms of emissions and converter longevity. If you have never replaced the valve stem oil seals, that will help reduce oil consumption. The bottom line is you will need a diagnostic, and scan tool, to determine what has to be optimized to reduce emissions. If you desire that, please simply request an engine diagnostic and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. My 4-cylinder S10 1999 failed on Cadillac converter slightly too warm not red.. it passed everything else.. no check engine light

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: 2002 Chevy Malibu won't start

The anti-theft indicator is supposed to come on for three seconds when the ignition key is cycled, then go out. Since you said the indicator went out, it doesn't sounds like the anti-theft system is the problem. If you have...

Q: No power to the fuel pump

Hi. I would go back over a few things. Specifically, the fuel pump relay and fuses. Check the voltage drop across the fuel pump relay while trying to start it. An older relay will pass a resistance test (the contacts...

Q: 1999 Honda CR-V door not opening from inside

Door handles on cars are connected to metal rods that actuate the latch causing the door to open. It is possible that one of the rods has become disconnected from the interior door handle causing it not to work. It...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.