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 Tim's Auto Repair Your Own Question

Tim's Auto Repair
Tim's Auto Repair, mechanic
Category: Chevy
Satisfied Customers: 13231
Experience:  Have owned a repair shop for 25 yrs.
14541291
Type Your Chevy Question Here...
Tim's Auto Repair is online now
A new question is answered every 9 seconds

A 2000 silverado truck..5.3l..coolant temperature sensor..O2 sensor

Resolved Question:

Recently asked a question about a 2000 silverado truck 5.3l thats hard to start when hot. I recieved an answer that said possible bad coolant temperature sensor or O2 sensor. I replaced 2 of the 4 o2 sensors and replaced the coolant tempereature sensor. Still hasn't fixed my problem. Any other suggestions?
Submitted: 3 years ago.
Category: Chevy
Expert:  Tim's Auto Repair replied 3 years ago.

hi

how many miles is on it?

does the engine light stay on?if so,can you give me the computer codes?

does the engine ever die out on you?

does it always start good cold?

what all have you tried?

please explain your problem to me the best you can

Customer: replied 3 years ago.

230k miles on it, I replaced the fuel pump last year, i replaced the fuel pressure regulator 2-3 months ago, check engine light is on and there is two codes p0420 and p0430. Truck starts great cold never cuts out has plenty of power. I have a hypertech power programmer on it. I have replaced sensor 1 bank 1 and sensor 2 bank 2. and the coolant temp sensor. Last week i rechagred air filter, cleaned MAF, and changed fuel filter. When truck gets up to running temp and is shut off and it is restarted within 15- 20 minutes of shutdown it will start without a problem. If it sits for longer then 20 minutes or so I have to pump the gas pedal to get it to start on the first try. Or i can let it turn over for 30 seconds until it finally starts.

Expert:  Tim's Auto Repair replied 3 years ago.

ok

the first thing to do here is to check the fuel pressure,these must have no less than 55psi at all times.test it when it wont start,just to make sure it isn't loosing pressure when it get s hot..............but,this sounds as if you may have a bad crank sensor,these will do this sometimes when they go bad,and not give a code for it...when these are breaking down with heat like this,testing the crank sensor may not help,,,replace it...the codes you are getting makes me think the catalyst converter may be bad,but,i don't think it is why the engine is not starting

thanks

 

 

 

 

 

 

 

ALL THE BONUS MONEY THAT I RECEIVE DURING THE MONTH OF JUNE WILL BE DONATED TO THE AMERICAN RED CROSS FOR TORNADO RELEIF IN THE MID WEST,NORTHEAST AND DEEP SOUTH,,THANKS FOR YOUR SUPPORT

 

P0420

 

Diagnostic Chart
Refer to Engine Controls Schematics PCM, CMP Sensor, CKP Sensor, KS, IPC.

CIRCUIT DESCRIPTION
In order to maintain a reasonably low emissions of Hydrocarbons (HC) , Carbon Monoxide (CO) , and Oxides Of Nitrogen (NOx) , the engine controls system uses a three-way catalytic converter. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas. This reaction converts them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The PCM monitors this process using bank 1 Heated Oxygen Sensor (HO2S) 2. bank 1 HO2S 2, located in the exhaust stream past the three-way catalytic converter, produces an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalysts ability to convert exhaust emissions effectively. If the catalyst is functioning correctly, the bank 1 HO2S 2 signal will be far less active than that produced by bank 1 HO2S 1. This indicates that the three-way catalytic converters oxygen storage capacity is operating at a threshold considered acceptable.

When the conditions for running this DTC are met, the following occurs:

 

  1. The Powertrain Control Module (PCM) captures the current rear HO2S rich or lean status.
  2. The air fuel ratio transitions from rich to lean or lean to rich depending on the capture rear HO2S rich or lean status.
  3. The air fuel ratio transitions a second time opposite the first air fuel ratio transition.
  4. The PCM captures the response time, the time the HO2S goes from below 300 mV to above 600 mV and from 600 mV to below 300 mV , of the front and rear heated oxygen sensors when the air fuel ratio transitions occurred.
  5. The PCM measures the time it takes the rear HO2S voltage to cross a reference rich or lean threshold minus the time it takes the front HO2S voltage to cross the same rich or lean threshold. The time difference from the front and rear HO2S is the oxygen storage capacity of the catalyst. This DTC sets if the time exceeds a predetermined threshold.

CONDITIONS FOR RUNNING THE DTC

  • No active Mass Air Flow (MAF) DTCs
  • No active Manifold Absolute Pressure (MAP) DTCs
  • No active Engine Coolant Temperature (ECT) DTCs
  • No active Intake Air Temperature (IAT) DTCs
  • No active Throttle Position (TP) DTCs
  • No active secondary Air Injection (AIR) DTCs
  • No active Crankshaft Position (CKP) sensor DTCs
  • No active Camshaft Position (CMP) sensor DTCs
  • No active Ignition Control DTCs
  • No active Idle Air Control (IAC DTCs
  • No active Exhaust Gas Recirculation (EGR) DTCs
  • No active Evaporative Emission (EVAP) DTCs
  • No active misfire DTCs
  • No active HO2S DTCs
  • No active fuel trim DTCs
  • No active injector DTCs
  • No active Vehicle Speed Sensor (VSS) DTCs
  • No active transmission DTCs
  • Engine operating longer than 400 seconds .
  • The ECT is between 80°C (176°F) and 120°C (248°F) .
  • The IAT is between -15°C (+5°F) and 75°C (167°F) .
  • Engine speed is more than 800 RPM for a minimum of 30 seconds (4.8L, 5.3L) or 40 seconds (6.0L) since the end of the last idle test.
  • The BARO is more than 74 kpa .
  • The fuel system is operating in Closed Loop.

CONDITIONS FOR SETTING THE DTC
The PCM determines the oxygen storage capability of the catalytic converter has degraded below a calibrated threshold.

ACTION TAKEN WHEN THE DTC SETS

  • The PCM illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
  • The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC

  • The PCM turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
  • A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
  • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
  • Use a scan tool in order to clear the MIL and the DTC.

TEST DESCRIPTION
The number below refers to the step number on the diagnostic table.

  1. Before replacing the three-way catalytic converter, correct any conditions which may have damaged the catalyst.

 

P0430

 

Diagnostic Chart
Refer to Engine Controls Schematics PCM, CMP Sensor; CKP Sensor, KS, IPC.

CIRCUIT DESCRIPTION
In order to maintain a reasonably low emissions of Hydrocarbons (HC) , Carbon Monoxide (CO) , and Oxides Of Nitrogen (NOx) , the engine controls system uses a three-way catalytic converter. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas. This reaction converts them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting it to nitrogen. The PCM monitors this process using bank 2 Heated Oxygen Sensor (HO2S) 2. bank 2 HO2S 2, located in the exhaust stream past the three-way catalytic converter, produces an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalysts ability to convert exhaust emissions effectively. If the catalyst is functioning correctly, the bank 2 HO2S 2 signal will be far less active than that produced by bank 2 HO2S 1. This indicates that the three-way catalytic converters oxygen storage capacity is operating at a threshold considered acceptable.

When the conditions for running this DTC are met, the following occurs:

 

  1. The Powertrain Control Module (PCM) captures the current rear HO2S rich or lean status.
  2. The air or fuel ratio transitions from rich to lean or lean to rich depending on the capture rear HO2S rich or lean status.
  3. The air fuel ratio transitions a second time opposite the first air fuel ratio transition.
  4. The PCM captures the response time, the time the HO2S goes from below 300 mV to above 600 mV and from 600 mV to below 300 mV , of the front and rear HO2S when the air fuel ratio transitions occurred.
  5. The PCM measures the time it takes the rear HO2S voltage to cross a reference rich or lean threshold minus the time it takes the front HO2S voltage to cross the same rich or lean threshold. The time difference from the front and rear HO2S is the oxygen storage capacity of the catalyst. This DTC sets if the time exceeds a predetermined threshold.

CONDITIONS FOR RUNNING THE DTC

  • No active Mass Air Flow (MAF) DTCs
  • No active Manifold Absolute Pressure (MAP) DTCs
  • No active Intake Air Temperature (IAT) DTCs
  • No active Engine Coolant Temperature (ECT) DTCs
  • No active Throttle Position (TP) DTCs
  • No active Exhaust Gas Recirculation (EGR) DTCs
  • No active Evaporative Emission (EVAP) DTCs
  • No active Vehicle Speed Sensor (VSS) DTCs
  • No active secondary Air Injection (AIR) DTCs
  • No active Crankshaft Position (CKP) sensor DTCs
  • No active Camshaft Position (CMP) sensor DTCs
  • No active Ignition Control (IC) DTCs
  • No active Idle Air Control (IAC) DTCs
  • No active Exhaust Gas Recirculation (EGR) DTCs
  • No active Evaporative Emission (EVAP) DTCs
  • No active misfire DTCs
  • No active Heated Oxygen Sensor (HO2S) DTCs
  • No active fuel trim DTCs
  • No active injector DTCs
  • No active transmission DTCs
  • Engine operating longer than 400 seconds .
  • The ECT is between 80°C (176°F) and 120°C (248°F) .
  • The IAT is between -15°C (+5°F) and 75°C (167°F) .
  • Engine speed is more than 800 RPM for a minimum of 30 seconds (4.8L, 5.3L) or 40 seconds (6.0L) since the end of the last idle test.
  • The BARO is more than 74 kpa .
  • The fuel system is operating in Closed Loop.

CONDITIONS FOR SETTING THE DTC
The PCM determines the oxygen storage capability of the catalytic converter has degraded below a calibrated threshold.

ACTION TAKEN WHEN THE DTC SETS

  • The PCM illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
  • The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC

  • The PCM turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
  • A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
  • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
  • Use a scan tool in order to clear the MIL and the DTC.

TEST DESCRIPTION
The number below refers to the step number on the diagnostic table.

  1. Before replacing the three-way catalytic converter, make sure that any conditions which may have caused the catalyst to be damaged have been corrected.

FUEL PRESSURE

Testing and Inspection

 

Diagnostic Chart (Part 1 Of 3)
Diagnostic Chart (Part 2 Of 3)
Diagnostic Chart (Part 3 Of 3)
Schematic
CIRCUIT DESCRIPTION
When you turn ON the ignition switch, the Powertrain Control Module (PCM) turns ON the in-tank fuel pump. The in-tank fuel pump remains ON as long as the engine is cranking or running and the PCM receives reference pulses. If there are no reference pulses, the PCM turns the in-tank fuel pump OFF 2 seconds after the ignition switch is turned ON or 2 seconds after the engine stops running.

The electric fuel pump attaches to the fuel sender assembly inside the fuel tank. The in-tank fuel pump supplies fuel through an in-pipe fuel filter to the fuel rail assembly. The fuel pump provides fuel at a pressure above the pressure needed by the fuel injectors. A fuel pressure regulator, attached to the fuel rail, keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel returns to the fuel tank by a separate fuel return pipe.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.

 

  1. When the ignition switch is ON and the fuel pump is running, the fuel pressure indicated by the fuel pressure gauge should read 379-427 kPa (55-62 psi) . The spring pressure inside the fuel pressure regulator controls the fuel pressure.
  2. A fuel system that drops more than 34 kPa (5 psi) in 10 minutes has a leak in one or more of the following areas:
    • The fuel pump check valve
    • The fuel pump flex pipe
    • The valve or valve seat within the fuel pressure regulator
    • The fuel injectors
  1. A fuel system that drops more than 14 kPa (2 psi) in 10 minute after being relieved to 69 kPa (10 psi) indicates a leaking fuel pump check valve.
  2. Fuel pressure that drops-off during acceleration, cruise, or hard cornering may cause a lean condition. A lean condition can cause a loss of power, surging, or misfire. You can diagnose a lean condition using a scan tool. It an extremely lean condition occurs, the heated oxygen sensors will stop toggling. The heated oxygen sensor output voltages will drop below 300 mV . The fuel injector pulse width will increase. IMPORTANT: Make sure the fuel system is not operating in the Fuel Cut-Off Mode. This can cause false indications by the scan tool.
  1. When the engine is at idle, the manifold pressure is low. This low pressure is applied to the fuel pressure regulator diaphragm. The low pressure will offset the pressure being applied to the fuel pressure regulator diaphragm by the spring inside the fuel pressure regulator. When this happens, the result is lower fuel pressure. The fuel pressure at idle will vary slightly as the barometric pressure changes, but the fuel pressure at idle should always be less than the fuel pressure noted in step 2 with the engine OFF.
  1. A rich condition may result from the fuel pressure being above 427 kPa (62 psi) . A rich condition may cause DTC P0132, DTC P0152, DTC P0172 or DTC P0175 to set. Driveability conditions associated with rich conditions can include hard starting followed by black smoke and a strong sulfur smell in the exhaust.
  2. This test determines if the high fuel pressure is due to a restricted fuel return pipe, or if the high fuel pressure is due to a faulty fuel pressure regulator.
  1. A lean condition may result from the fuel pressure being below 379 kPa (55 psi) . A lean condition may cause DTC P0131, DTC P0151, DTC P0171, or DTC P0174 to set. Driveability conditions associated with lean conditions can include hard starting, hesitation, poor driveability, lack of power, surging, and misfiring.
  2. Restricting the fuel return pipe with the fuel pipe shut-off adapter causes the fuel pressure to rise above the regulated fuel pressure. Using a scan tool to pressurize the fuel system, the fuel pressure should rise above 427 kPa (62 psi) as the valve on the fuel pipe shut-off adapter connected to the fuel return pipe becomes partially closed.
  1. Check the spark plug associated with a particular fuel injector for fouling or saturation in order to determine if that particular fuel injector is leaking. If checking the spark plug associated with a particular fuel injector for fouling or saturation does not determine that a particular fuel injector is leaking, use the following procedure:
  1. Remove the fuel rail.
  2. Reinstall the crossover pipe to the right fuel rail.
  3. Connect the fuel feed pipe and the fuel return pipe to the fuel rail.
  4. Lift the fuel rail just enough to leave the fuel injector nozzles in the fuel injector ports.
  5. Pressurize the fuel system by using the scan tool fuel pump enable.
  6. Visually and physically inspect the fuel injector nozzles for leaks.

 

Crankshaft Position (CKP) Sensor Replacement

REMOVAL PROCEDURE

CAUTION: Before servicing any electrical component, the ignition key must be in the OFF or LOCK position and all electrical loads must be OFF, unless instructed otherwise in these procedures. If a tool or equipment could easily come in contact with a live exposed electrical terminal, also disconnect the negative battery cable. Failure to follow these precautions may cause personal injury and/or damage to the vehicle or its components.

IMPORTANT: Perform the CKP System Variation Learn Procedure when the crankshaft position sensor is removed or replaced.


 

  1. Disconnect the negative battery cable.
  2. Raise the vehicle.
  3. Remove the starter.

 


 

  1. Disconnect the Crankshaft Position (CKP) sensor electrical connector.

 


 

  1. Clean the area around the CKP sensor before removal in order to avoid debris from entering the engine.
  2. Remove the CKP sensor retaining fastener.
  3. Remove the CKP sensor.

INSTALLATION PROCEDURE


 

  1. Install the CKP sensor.
  2. Install the CKP sensor retaining fastener. Tighten Tighten the fastener to 25 N.m (18 lb ft) .

 


 

  1. Connect the CKP sensor electrical connector.

 


 

  1. Install the starter.
  2. Lower the Vehicle.
  3. Connect the negative battery cable.

 

 

 

 

 

 

 

ALL THE BONUS MONEY THAT I RECEIVE DURING THE MONTH OF JUNE WILL BE DONATED TO THE AMERICAN RED CROSS FOR TORNADO RELEIF IN THE MID WEST,NORTHEAST AND DEEP SOUTH,,THANKS FOR YOUR SUPPORT

Customer: replied 3 years ago.

If this doesnt work how can i get back in touch with you?

Expert:  Tim's Auto Repair replied 3 years ago.

yes,i will leave it open

thanks

Please ACCEPT my answer so I can get credit for my work.i don't receive commission unless you do ..I'm not always going to be giving you good news,so please don't let this stand in the way of you accepting my answer.it does not cost you more money.we will still be able to communicate.. Bonuses and positive feedback are appreciated!if you are not satisfied with my answer,please do not leave bad feed back,i will gladly opt out and let another expert handle the question.if i have sent any diagrams,please print them.they will only stay on here for an hour or so.PLEASE ASK IF YOU NEED MORE HELP

 

 

 

 

 

 

 

ALL THE BONUS MONEY THAT I RECEIVE DURING THE MONTH OF JUNE WILL BE DONATED TO THE AMERICAN RED CROSS FOR TORNADO RELEIF IN THE MID WEST,NORTHEAST AND DEEP SOUTH,,THANKS FOR YOUR SUPPORT

Tim's Auto Repair, mechanic
Category: Chevy
Satisfied Customers: 13231
Experience: Have owned a repair shop for 25 yrs.
Tim's Auto Repair and 4 other Chevy Specialists are ready to help you

JustAnswer in the News:

 
 
 
Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.
 
 
 

What Customers are Saying:

 
 
 
  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
< Last | Next >
  • I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money. Todd L Rochester NY
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C. Freshfield, Liverpool, UK
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex Los Angeles, CA
  • Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult. GP Hesperia, CA
  • I couldn't be more satisfied! This is the site I will always come to when I need a second opinion. Justin Kernersville, NC
  • Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around. Esther Woodstock, NY
  • Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know. Robin Elkton, Maryland
 
 
 

Meet The Experts:

 
 
 
  • Tim's Auto Repair

    mechanic

    Satisfied Customers:

    7641
    Have owned a repair shop for 25 yrs.
< Last | Next >
  • http://ww2.justanswer.com/uploads/TI/tim37857/2011-10-28_23053_S6301814.64x64.JPG Tim's Auto Repair's Avatar

    Tim's Auto Repair

    mechanic

    Satisfied Customers:

    7641
    Have owned a repair shop for 25 yrs.
  • http://ww2.justanswer.com/uploads/DT/dt69nova/2012-6-15_234154_pic1.64x64.jpg Dave Nova's Avatar

    Dave Nova

    Chevrolet Technician

    Satisfied Customers:

    6870
    ASE Master Certification. GM World Class Certification
  • http://ww2.justanswer.com/uploads/ggrote1/2009-06-27_031011_me.jpg Gary's Avatar

    Gary

    Chevy Technician

    Satisfied Customers:

    5404
    15 years GM master tech
  • http://ww2.justanswer.com/uploads/testedtuff/2009-09-26_170108_pictures.jpg John's Avatar

    John

    Master A.S.E Automotive technician

    Satisfied Customers:

    4071
    A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
  • http://ww2.justanswer.com/uploads/RO/rodcuda/2011-7-25_224114_Donhoff1.64x64.JPG Neal's Avatar

    Neal

    Chevy Mechanic

    Satisfied Customers:

    2306
    Shop Owner and Mechanic on multiple makes.
  • http://ww2.justanswer.com/uploads/goodwrench9124/2008-11-09_220838_dscf0007.jpg goodwrench9124's Avatar

    goodwrench9124

    ASE Certified Technician

    Satisfied Customers:

    2041
    Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer, Hybrid certified
  • http://ww2.justanswer.com/uploads/DR/drivefast1971/2012-1-12_172422_0009051tQKh.64x64.jpg Ron Z.'s Avatar

    Ron Z.

    - Chevy Tech -

    Satisfied Customers:

    1912
    18+yrs experience. State Inspector and Chevy Diagnostics
 
 
 
Chat Now With A Chevy Mechanic
Tim's Auto Repair
Tim's Auto Repair
Mechanic
7864 Satisfied Customers
Have owned a repair shop for 25 yrs.