Toyota Nation Forum banner
1 - 16 of 16 Posts

·
Registered
Joined
·
108 Posts
Discussion Starter · #1 ·
CHK ENGINE LIGHT

For every motorist it is most annoying :sosad: if “CHECH ENGINE” yellow light pops-up while driving along. It is the most misunderstood indicator on your dashboard, the "check engine" light can mean many different things, from a loose gas cap to a seriously malfunctioning engine loosing power.

You do not have to pull the car over to the side of the road and call a tow truck. Still you can drive your car safely. But, you should get the car checked professionally for engine relate fuel system, cooling system, exhaust system, EGR system and EVAP system, as soon as possible. Ignoring this warning, may lead you end up damaging engine or degrading performance by loosing fuel economy and emitting higher levels of pollutants.

Here are some simple steps for Do-It-Yourself….:confused:
Just simply do not throw parts one-by-one, make sure it is faulty before you replace. If you do not know how to check particular component, ask :ugh3: , some one will definitely help you out here.

In Toyota Corolla, there are certain sensors inputs to ECU Engine Control Unit which can trigger "Check Engine". These are....

Engine coolant Temperature sensor
Mass Air flow sensor
Crank shaft Position Sensor
Throttle position sensor
Park / neutral gear Selector Position
Vehicle Speed Sensor
Knock Sensor
Power steering Oil Pressure
Intake Air Sensor
Fuel / Vapor Pressure
Absolute Manifold Pressure
Oxygen / Air-fuel Ratio Sensor

EGR –Flow / Temperature Sensor

If you can start and steer your car well and smoothly from extreme right and left, but, still inspect for power steering fluid loss or leakage. If, still Check Engine light remains on you should target last three sensors. Possible causes are:


1. improper fuel pressure.
Leak in fuel system, may be pin-hole, To detect this fill-up your tank to the maximum, park your car in a clean space for a while 5 to 10 min. and check the for the fuel leak on the bottom, if there is any, may be because of loose Gas Cap, Fuel intake pipe, Gas Tank or Fuel lines.


2. Leak in Exhaust system. Can be detected and fixed very easy.


3. Fuel injector restricted. Use Fuel Injector Cleaner several times.

4. Engine coolant Temperature sensor (DCT Code : P0115)
Check Engine Cooling Sytem and radiator circuit for any possible leakage.
Inspect Radiator and hoses connection for leaks. Keep checking level of radiator coolant very often. If there is no leak...

A thermistor built into the engine coolant temp. sensor changes the resistance value according to the engine
coolant temp.

DTC - P0115 Open or short in engine coolant temp. sensor circuit
-Open or short in engine coolant temp. sensor circuit
-Engine coolant temp. sensor
Follow these steps.
(a) Disconnect the engine coolant temperature sensor connector.
(b) Connect the terminals 1 with 2 of the engine coolant temperature
sensor connector. Measure the resistance between terminal 1 and 2. check for open circuit or short circuit. Ideally it should read between 2.0 Kohms to 3.0 Kohms.
(c) Turn the ignition switch ON. Start the vehicle.
(d) Measure the resistance between terminal 1 and 2. As the coolant temperature starts rising up, the resistance starts falling down. At 180 deg C it should read approximately 0.2 Kohms, depends on make.

If the ECM detects the DTC P0115, it operates fail safe function in which the engine coolant temperature is assumed to be 80_C (176_F).

5. EGR – Exhaust Gas Recycle (DTC Code: 71 or P0401)
EGR system reduces NOx output by re-circulating portion of exhaust gases with normal air-to-fuel charge in the engine. EGR Flow is higher while cruising and mid-range acceleration when typical combustion temperature is very high. At lower speed and light load condition lower EGR flow is required. No EGR flow is required while idling or engine warm-up. There are four major components in EGR system, EGR Valve, EGR Vacuum Modulator, VSV: ECU controlled Vacuum Switching Valve and EGR Gas Temperature Sensors plus piping. With the age of the vehicle, EGR system problem is very common.

Use this routine:


-Remove the EGR Vacuum Modulator from the holding clamp and open the top cap. Inspect and replace the filter if required. Diesel (without any rust inhibitor additives or contents) can be used for removal of carbon deposits in the piping.

-Remove the EGR Valve from the mount. Remove the EGR inlet and outlet pipes from the exhaust manifold and the intake manifold. Blow air in inlet port and check for external and internal leaks. Inspect and replace the gasket if required. Inspect the manifold EGR ports and the EGR inlet and outlet pipes for a blockage caused by excessive deposits, casting flashing or other damage. Diesel (without any rust inhibitor additives or contents) can be used for removal of carbon deposits in the piping (A heavy guitar string on a drill motor works real good for running thru the manifold passage to open up the port). Then re-install the EGR and road-test again and also try cruise control at various speeds. If the light doesn't come on, you know that was the problem.
-Check EGR Temperature Sensor.
- Check and clean inlet and out let ports plus electrical connector of EGR VSV. ECU uses three signals to control the operation of EGR VSV switch --- distributor signal, coolant temperature signal and vacuum pressure signal. So after carrying out EGR system maintenance, you should service clean up for distributor cap and clan up electrical contacts of distributor, engine coolant temp sensor and vacuum sensors.
Again, with the age of the vehicle, this is very common.

6. Defective heated Main oxygen sensor No. 1. (DTC code: P0130, P0133, P0420)
If you are very sure about 1, 2, 3, 4 and 5 then target main oxygen sensor located after exhaust manifold and before catalytic converter. This oxygen sensor provides ECU feedback of the oxygen contents in the exhaust gas. The ECU uses this feedback to maintain proper air-to-fuel ratio. The main O2 sensor voltage should vary fairly rapidly between about 200mV and 800mV. After replacement disconnect battery positive terminal for a while and reconnect it. Start the car and see if Check Engine light turns on. Replacing oxygen sensor from the top requires 22mm or 7/8 slotted socket, but, still can be replaced with precision by 22mm open-end line wrench accessing from bottom.


If Check Engine light turns on. After a while, replace sub oxygen sensor (DTC code: P0421) located after catalytic converter and before exhaust tail pipe. This sub-oxygen sensor is slower in response than main one and does not contribute to air-to-fuel ratio. However, ECU uses this feedback for proper functioning of catalytic converter. This sub-oxygen sensor should hold fairly steady around 500mV. After replacement disconnect battery positive terminal for a while and reconnect it. Start the car and see if Check Engine light turns on after a while target following sensors in sequence.

7. Defective Manifold Absolute Pressure (MAP) sensor.
8. Defective Engine Coolant Temperature (ECT) sensor.

99.9% your problem will be solved at either step 4, step 5 or at step6.


The purpose is served, if it can save your expensive charges for autoshop diagnosis. :)

I am posting this because some one posted very helpful list of OBD-II codes for ready refence and othe community member supplied me information what I was looking for. Personally, I found this community :whatwhat: GREAT!!!:clap:
 

·
Registered
Joined
·
937 Posts
Id say about 85-90% of the check engine lights we see here are Evaporative system codes. Usually due to a leak in the system or a solenoid <vsv> not functioning properly. Thats for all manufacturers.
 

·
Registered
Joined
·
108 Posts
Discussion Starter · #4 ·
EVAP System details requested

Hi ShawnM,

Thanx A Lot for completing me for what I missed.

Furthermore, I would like you to complete the thread by providing detals of EVAP system, EVAP components, EVAP related DTC codes and maintenance procedure.

I can also appreciate, if any of our community member can provide me details of EVAP system, component location and maintenance procedure to email id# [email protected]

Thanking you once again for your professional openion.

reg
bonnie*
 

·
Registered
Joined
·
108 Posts
Discussion Starter · #5 ·
Evap System Diagnosis

EVAP System
DTC Codes : P0440 THRU’ P0455

EVAP (Evaporative Emission Control System) is fully closed system which maintains stable fuel pressure in the system for proper functioning of fuel injectors and engine. properly. It prevents fuel vapors created in gas tank to escape to the atmosphere.

Cars manufactured after 1995, normally uses ECM controlled EVAP System. The major components of this system are:

1) Gas Cap with Vacuum Check Valve
2) Fuel Inlet Filler Pipe
3) Gas Tank
4) Fuel Lines
5) Charcoal Canister with vacuum & pressure check valve
6) VSV : Vacuum Switching Valve
7) P-Port : Ported Vacuum Purge Port on throttle body.

Leak or clogging in EVAP system can trigger “Check Engine” Light on. ECU can generate any of following codes depend upon nature of fault.

P0434 Heated Catalyst Temperature Below Threshold (Bank #2)
P0440 Evaporative Emission Control System Malfunction
P0441 Evaporative Emission Control System Incorrect Purge Flow
P0442 Evaporative Emission Control System Leak Detected (Small Leak)
P0443 Evaporative Emission Control System Purge Control Valve Circuit Malfunction
P0444 Evaporative Emission Control System Purge Control Valve Circuit Open
P0445 Evaporative Emission Control System Purge Control Valve Circuit Shorted
P0446 Evaporative Emission Control System Vent Control Circuit Malfunction
P0447 Evaporative Emission Control System Vent Control Circuit Open
P0448 Evaporative Emission Control System Vent Control Circuit Shorted
P0449 Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction
P0450 Evaporative Emission Control System Pressure Sensor Malfunction
P0451 Evaporative Emission Control System Pressure Sensor Range/Performance
P0452 Evaporative Emission Control System Pressure Sensor Low Input
P0453 Evaporative Emission Control System Pressure Sensor High Input
P0454 Evaporative Emission Control System Pressure Sensor Intermittent
P0455 Evaporative Emission Control System Leak Detected (Gross Leak)


Fault Diagnosis:

Visually inspect Gas Cap (check valve) gasket, Inlet Fuel Filler Pipe, Gas Tank and Fuel Lines for visible leak.

Check Charcoal Canister and TVV / VSV

MOST COMMON (HIGH OCCURANCE) CODES OUT ALMOST 2000 CODES FOR CHECK ENGINE LIGHTS ARE:

P0115 Engine Coolant Temperature Circuit Malfunction
P0125 Insufficient Coolant Temperature For Closed Loop Fuel Control
P0130 O2Circuit Malfunction (Bank #1 Sensor #1)
P0135 O2Sensor Heater Circuit Malfunction (Bank #1 Sensor #1)
P0136 O2Sensor Circuit Malfunction (Bank #1 Sensor #2)

P0170 Fuel Trim Malfunction (Bank #1)
P0171 System Too Lean (Bank #1)

P0200 Injector Circuit Malfunction
P0400 Exhaust Gas Recirculation Flow Malfunction
P0401 Exhaust Gas Recirculation Flow Insufficient Detected

P0420 Catalyst System Efficiency Below Threshold (Bank #1)
P0440 Evaporative Emission Control System Malfunction
P0442 Evaporative Emission Control System Leak Detected (Small Leak)

----------------------------- * - * - *----------------------------------------------------------
 

·
Registered
Joined
·
108 Posts
Discussion Starter · #6 ·
Reply to noahedvalson

Quote from Reply to noahedvalson: "
MAF sensor for P0171 code
Greetings fellow Corolla owners. I have a 2000 LE w/ about 73K on it. Last week I got the P0171 code, so after reading several forums, I cleaned the MAF sensor, replaced oil and air filter, then reset the code. The light came back on with same code within ten miles. I read a thread where one owner cleaned the sensor and even checked it w/ a meter, but everything checked out OK. He replaced the sensor anyway, and it fixed the problem. I am thinking that replacing the sensor is my best bet at this point, so I am wondering if it matters what kind I get. Dealership wants 160 bucks, while I can get a refurbed Cardone brand from Schucks or Autozone for 80. Does anyone know of possible complications with getting the aftermarket one?"

Reply:

DTC code P0171 : P0171 System Too Lean (Bank #1) always does not relate to MAF Sensor.
This code is generated and recorded when air-to fuel ratio feedback is stable for more than two scan cycle. This will trigger "CHECK ENGINE" LIGHT ON.

You have to check following things:
1) Blockage in Fuel Injection system & EFI relay.
2) MAF Sensor.
3) Low fuel pressure or Gas leakage in exhaust system.
4) Open or Short in Main Heated Pre-Catalyst Oxygen Sensor (Bank 1, Sensor 1)
5) PCV Valve and hose.

If you do nor know how to check, please ask, someone will help you out here.
I suspect 1), 4) and 5).


Or if you identify the cause by now, Please provide you complete feedback that how you solved it.

Thanx
bonnie*

p.s: JUST DO NOT SIMPLY THROW NEW PARTS IN SYSTEM, ONE BY ONE.
CHECK AND MAKE SURE IT'S FAULTY BEFORE YOU REPLACE.
 

·
Registered
Joined
·
9 Posts
I have a 2003 Toyota Corolla with 172000 miles. It's check engine is on. The code it shows is telling that catalytic converter is bad. I reset the light but did not drive long enough and took to a smog station for test. It passed all the smog related tests almost like a new car but failed for then check engine light test because it was reset and so called " readiness flags" were set and codes not there.

My question is that if the car is passing the smog test then why the code is telling me to replace catalytic converter which is functioning OK? Is there anything else to look for to correct this problem?

I will appreciate any help in this regard.

Thanks a lot.
 

·
Registered
Joined
·
3 Posts
I have a 06 xb and I'm having the same issue. Checked the ecu with torque pro and found a code p0134 and it erased on its own and now I have a code p0171. Car has a cold air intake and exhaust headers only. I have replaced the maf sensor only.
 

·
Registered
Joined
·
3 Posts
1. Can a small exhaust leak cause the p0171 to pop up and give me a lean mixture?
2. If my O2 sensor is bad causing me to get a p0171 why does the code P0134 continue to show when I check for codes? Any suggestions or tips on how to physically test the sensores would be appriciated.
 

·
Registered
Joined
·
3 Posts
Thanks for the reply. Well as for my case it's the eBay CAI I installed. I think that it just takes in to much air for the stock MAF to learn the new mod. I tried everything possible to fix the problem. I just went back to the stock air box and mod that. As of today no engine light. I still want to instal a CAI but this time I think I will go with K&N. Anyone have good stock air box mods they would like to post?
 

·
Registered
Joined
·
1 Posts
Same here. Had an E Check based on code reset (P0420) requiring full measuring and it passed. I would like to know how your problem was resolved and if the emissions check passed whether that means I can eliminate the cat.
 

·
Registered
Joined
·
2 Posts
CHK ENGINE LIGHT

For every motorist it is most annoying :sosad: if “CHECH ENGINE” yellow light pops-up while driving along. It is the most misunderstood indicator on your dashboard, the "check engine" light can mean many different things, from a loose gas cap to a seriously malfunctioning engine loosing power.

You do not have to pull the car over to the side of the road and call a tow truck. Still you can drive your car safely. But, you should get the car checked professionally for engine relate fuel system, cooling system, exhaust system, EGR system and EVAP system, as soon as possible. Ignoring this warning, may lead you end up damaging engine or degrading performance by loosing fuel economy and emitting higher levels of pollutants.

Here are some simple steps for Do-It-Yourself….:confused:
Just simply do not throw parts one-by-one, make sure it is faulty before you replace. If you do not know how to check particular component, ask :ugh3: , some one will definitely help you out here.

In Toyota Corolla, there are certain sensors inputs to ECU Engine Control Unit which can trigger "Check Engine". These are....

Engine coolant Temperature sensor
Mass Air flow sensor
Crank shaft Position Sensor
Throttle position sensor
Park / neutral gear Selector Position
Vehicle Speed Sensor
Knock Sensor
Power steering Oil Pressure
Intake Air Sensor
Fuel / Vapor Pressure
Absolute Manifold Pressure
Oxygen / Air-fuel Ratio Sensor

EGR –Flow / Temperature Sensor

If you can start and steer your car well and smoothly from extreme right and left, but, still inspect for power steering fluid loss or leakage. If, still Check Engine light remains on you should target last three sensors. Possible causes are:


1. improper fuel pressure.
Leak in fuel system, may be pin-hole, To detect this fill-up your tank to the maximum, park your car in a clean space for a while 5 to 10 min. and check the for the fuel leak on the bottom, if there is any, may be because of loose Gas Cap, Fuel intake pipe, Gas Tank or Fuel lines.


2. Leak in Exhaust system. Can be detected and fixed very easy.


3. Fuel injector restricted. Use Fuel Injector Cleaner several times.

4. Engine coolant Temperature sensor (DCT Code : P0115)
Check Engine Cooling Sytem and radiator circuit for any possible leakage.
Inspect Radiator and hoses connection for leaks. Keep checking level of radiator coolant very often. If there is no leak...

A thermistor built into the engine coolant temp. sensor changes the resistance value according to the engine
coolant temp.

DTC - P0115 Open or short in engine coolant temp. sensor circuit
-Open or short in engine coolant temp. sensor circuit
-Engine coolant temp. sensor
Follow these steps.
(a) Disconnect the engine coolant temperature sensor connector.
(b) Connect the terminals 1 with 2 of the engine coolant temperature
sensor connector. Measure the resistance between terminal 1 and 2. check for open circuit or short circuit. Ideally it should read between 2.0 Kohms to 3.0 Kohms.
(c) Turn the ignition switch ON. Start the vehicle.
(d) Measure the resistance between terminal 1 and 2. As the coolant temperature starts rising up, the resistance starts falling down. At 180 deg C it should read approximately 0.2 Kohms, depends on make.

If the ECM detects the DTC P0115, it operates fail safe function in which the engine coolant temperature is assumed to be 80_C (176_F).

5. EGR – Exhaust Gas Recycle (DTC Code: 71 or P0401)
EGR system reduces NOx output by re-circulating portion of exhaust gases with normal air-to-fuel charge in the engine. EGR Flow is higher while cruising and mid-range acceleration when typical combustion temperature is very high. At lower speed and light load condition lower EGR flow is required. No EGR flow is required while idling or engine warm-up. There are four major components in EGR system, EGR Valve, EGR Vacuum Modulator, VSV: ECU controlled Vacuum Switching Valve and EGR Gas Temperature Sensors plus piping. With the age of the vehicle, EGR system problem is very common.

Use this routine:


-Remove the EGR Vacuum Modulator from the holding clamp and open the top cap. Inspect and replace the filter if required. Diesel (without any rust inhibitor additives or contents) can be used for removal of carbon deposits in the piping.

-Remove the EGR Valve from the mount. Remove the EGR inlet and outlet pipes from the exhaust manifold and the intake manifold. Blow air in inlet port and check for external and internal leaks. Inspect and replace the gasket if required. Inspect the manifold EGR ports and the EGR inlet and outlet pipes for a blockage caused by excessive deposits, casting flashing or other damage. Diesel (without any rust inhibitor additives or contents) can be used for removal of carbon deposits in the piping (A heavy guitar string on a drill motor works real good for running thru the manifold passage to open up the port). Then re-install the EGR and road-test again and also try cruise control at various speeds. If the light doesn't come on, you know that was the problem.
-Check EGR Temperature Sensor.
- Check and clean inlet and out let ports plus electrical connector of EGR VSV. ECU uses three signals to control the operation of EGR VSV switch --- distributor signal, coolant temperature signal and vacuum pressure signal. So after carrying out EGR system maintenance, you should service clean up for distributor cap and clan up electrical contacts of distributor, engine coolant temp sensor and vacuum sensors.
Again, with the age of the vehicle, this is very common.

6. Defective heated Main oxygen sensor No. 1. (DTC code: P0130, P0133, P0420)
If you are very sure about 1, 2, 3, 4 and 5 then target main oxygen sensor located after exhaust manifold and before catalytic converter. This oxygen sensor provides ECU feedback of the oxygen contents in the exhaust gas. The ECU uses this feedback to maintain proper air-to-fuel ratio. The main O2 sensor voltage should vary fairly rapidly between about 200mV and 800mV. After replacement disconnect battery positive terminal for a while and reconnect it. Start the car and see if Check Engine light turns on. Replacing oxygen sensor from the top requires 22mm or 7/8 slotted socket, but, still can be replaced with precision by 22mm open-end line wrench accessing from bottom.


If Check Engine light turns on. After a while, replace sub oxygen sensor (DTC code: P0421) located after catalytic converter and before exhaust tail pipe. This sub-oxygen sensor is slower in response than main one and does not contribute to air-to-fuel ratio. However, ECU uses this feedback for proper functioning of catalytic converter. This sub-oxygen sensor should hold fairly steady around 500mV. After replacement disconnect battery positive terminal for a while and reconnect it. Start the car and see if Check Engine light turns on after a while target following sensors in sequence.

7. Defective Manifold Absolute Pressure (MAP) sensor.
8. Defective Engine Coolant Temperature (ECT) sensor.

99.9% your problem will be solved at either step 4, step 5 or at step6.


The purpose is served, if it can save your expensive charges for autoshop diagnosis. :)

I am posting this because some one posted very helpful list of OBD-II codes for ready refence and othe community member supplied me information what I was looking for. Personally, I found this community :whatwhat: GREAT!!!:clap:
when you refer to the coolant temp.sensor ! its a 2 pin connector or 3 pin connector???
 

·
Registered
Joined
·
9 Posts
Thought it was logical to read the DTC codes when CEL lights up, Bought a MVIC cable and checked it work well with a 02 Camry, only to find a more serious error: Techstream report "Cannot establish communication with the ECU" on 09 Corolla 2ZE. Any tips for next troubleshooting step besides replacing the ECU?
 
1 - 16 of 16 Posts
Top