How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Roy Your Own Question
Roy, import/domestic specialest
Category: Car
Satisfied Customers: 6181
Experience:  ASE master tech for 40 years
Type Your Car Question Here...
Roy is online now
A new question is answered every 9 seconds

Hyundai Elantra GT: 03 Huyundai elantra Gt ca emissions- codes

This answer was rated:

03 Huyundai elantra Gt ca emissions- codes P0030 and P2251. O2 sensor heater not funcitioning due to open ground circuit. Connector pin 6 has no ground when ignnition is on. Where is the relay to ground?
good evening my name is XXXXX XXXXX I will help you tonight

Did you measure the voltage on the ground wire at the sensor????

what is the voltage??? the pcm controls the ground, there is no relay. the pcm will ground the heater circuit when the engine is cold on start up to get the sensor up to temp. after about a minute it will not ground anymore till it is needed.

Customer: replied 3 years ago.


The voltage at pin 5 power input is 12 volts with the battery voltage at 12.47.

There was no voltage on pin 6 the ground side, but the resistance to ground today was 361 ohms. These readings were all taken at the harness side connector with the sensor disconnected. I erased the codes and got the check engine light again, but the code was only P0030.


With a warm engine the resistance measured between pins 5 and 6 on the sensor was 4 ohms.


You asked for the voltage on the ground wire at the sensor. Do you want me to penetrate the wire insulation to get a reading while it was connected to the harness?




you have the needed voltage at the o2 heater portion. I would replace the sensor as the heater portion has failed.

when a code returns immediately after clearing, you have an electrical failure such as the heater in the sensor. I feel confident from your readings that you have a failed sensor.

Customer: replied 3 years ago.


Ok, I will install a new sensor and let you know the results.


ok, let me know
Roy and 6 other Car Specialists are ready to help you
Customer: replied 3 years ago.

New o2 OEM type sensor was installed. Check engine light is now out.

wonderfull. good job.