Code PO455

Tiny
MIKEWALLACE19
  • MEMBER
  • 2006 CHEVROLET TRAILBLAZER
  • 4.2L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
My moms car quit running I ran my diagnostic tool on it and came back with a po455. Evap gross leak/no flow. Replaced gas cap did not fix, pulled the purge valve solenoid and it was stuck shut. Replaced the purge valve solenoid vehicle started and ran well. Cleared code and returned car to my mother three days later the check engine light reappears and car stops running. So now I run the codes again and it shows up with the original po455, but now also shows po141 which is o2 heater sensor bank 1 sensor 2, and also reads po135 o2 heater sensor bank 1 sensor 2. I need help I do not know why both sensors would fail simultaneously is this a symptom of something going wrong in the Evap system? She cannot afford to take it to a shop and the car I am letting her use for now is falling apart. I need help!
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Wednesday, June 14th, 2017 AT 3:01 PM

3 Replies

Tiny
STEVE W.
  • EXPERT
P0141/P0135 are both heater circuit codes. Look around the sensors and up to the front of the truck for a broken or damaged wire/wires that power the O2 heaters. Not uncommon to see them hit the exhaust or rub on a sharp corner and damage the wires in the harness.

As for the P0455, the best way to find those it to use a smoke machine. If you don't have one you will need to test each section of the system. Start with the EVAP vent solenoid under the truck near the canister. They love to stick open and create a big hole.
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Thursday, June 15th, 2017 AT 10:46 PM
Tiny
MIKEWALLACE19
  • MEMBER
Will defiantly trace the wires back to the harness and as far as the po455 I replaced the purge valve solenoid and the canister vent valve so its either the fuel filler neck or a leak somewhere in the line that I cannot see. Also, do you by chance know if there is a different code for a failed fuel pump? I am only getting those three codes but this year/model has the fuel filter inside the fuel pump and is not changeable you have to replace the whole pump if it is clogged and when the engine is cranking there is no smell of fuel in the exhaust.
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Friday, June 16th, 2017 AT 9:06 AM
Tiny
STEVE W.
  • EXPERT
No code for a failed pump but there are codes that can point to a bad or failing pump. For instance fuel trim numbers showing a lean condition, or a P0451 Fuel pressure sensor performance, or a P0300 Random Misfire could all point to a pump on it's way out. You can also test the amount of current the pump is drawing as a clue.

Normally you won't smell fuel in the exhaust on most newer vehicles, if there is a fault that stops the engine from actually starting the ECM will shut off the pump and injectors.

The basic way it works - Turn key to start, as soon as the run contact closes it turns the fuel pump on for initial prime. Keep turning key to start and the starter engages. The ECM looks at the cam and crank sensors to determine which cylinder is coming up on compression and starts triggering the ignition for that cylinder. It then monitors the cam signal, oil pressure and tach signal. IF the engine fires and the rpm and oil pressure starts to rise it turns the pump relay on and the engine runs.

IF however the engine doesn't start and the tach signal doesn't rise the pump may not be activated. The ECM doesn't want raw fuel in the convertor. That is the ECMs primary job, to keep the convertor(s) alive through fuel/air control.

In your case the EVAP leak won't cause it to fail to run. Neither would the O2 heater code ON IT'S OWN. What I suspect you will find will be that the wiring is damaged and the reference voltage to the sensor is also grounding out along with the heater wires. That reference voltage is used by other sensors, no voltage to them and the engine doesn't run.

For a LOT more information I would suggest you get a subscription to either Alldata or Mitchell for that vehicle. It runs about 30 dollars for a years access and gives you the same repair information as the pros use, as well as giving you the wiring diagrams and code definitions and the parameters that set them.
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Sunday, June 18th, 2017 AT 4:15 AM

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