Question about 1994 Toyota Previa

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I have a 1994 Toyota previa. It failed emmissions test with an egr code. EGR has been changes, vacuum line has been checked for leaks, egr thermal switch has been changed. Still has an egr code. is it possible for a 16 year old catalytic convertor to be the problem without throwing the code for it? Could the reading be a malfunction. code is DTC71, egr system malfunction-

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My 1996 has had the P040 code (EGR insufficient flow) for years and years. I suspect the EGR modulator has failed, but have not had to fix it, because it drives just fine and I don't live in a place that needs emissions testing. My Chilton's manual has details how to test the whole EGR system and each component. I recommend buying a manual and going through the testing systematically rather than trying new parts randomly. The manual is usually around $20 at any autoparts store (or ebay).

Posted on Dec 19, 2017

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6ya6ya
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Posted on Jan 02, 2017

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SOURCE: Difficulty to replace EGR valve in 1999 totyota camry 4-cyl automatic

If you have small hands it can be easy. The space between firewall and EGR is tight but it wasn't too difficult to remove. The vacuum hose at the bottom was hard to pull off and I ended up cracking it and had to splice it. It was more difficult to re-install the EGR then remove it. I had a difficult time with keeping the gasket aligned while bolting it in to the lower tube. I took a few attempts. I suggest when replacing the EGR leave the mounting bolts loose so you can more easily align the metal tube. I would tighten the metal tube at the bottom of EGR first then tighten the upper two mounting bolts on top. It took me about 5 minutes to remove and 15 minutes to replace. I would be sure to clean the IAC too after cleaning the EGR. I sprayed throttle bottle cleaner down the bottom hole located on the throttle body and let soak about 15 minutes then start and run the engine a minute and repeat the process. This helped smooth the idle while stopped at a light. It also stopped the idle from shaking and almost stalling the car out at a traffic stop when the engine was warm.

Posted on Jul 10, 2008

motor1258
  • 6674 Answers

SOURCE: OBD code 0401 (1997 Toyota Camry 4 cyl)

There is a VSV (vacuum switching valve) , usually mounted on the back side of engine block, under the intake manifold, as well as the map sensor, that can also cause that code if one or the other is faulty. It takes some pretty detailed troubleshooting to confirm this in some cases, so if that's not in your line of work, you may have to have it properly diagnosed, or take a 50/50 shot at which one first.

Posted on Jan 24, 2009

jgwhomeequip
  • 1902 Answers

SOURCE: egr valve on a 99 saturn sl

Take it off and look at it internally, See if you can move the diaphragm if not then it needs replacement. But you should just go ahead and replace it anyways since it is a 99 it would just be worth it

Posted on Feb 11, 2009

emissionwiz
  • 85178 Answers

SOURCE: DTC Code of a 1404 , and also a IAT High input malfunction

sounds like the IAT is disconnected, it is either in the flex hose from the air cleaner to the engine or in the air filter housing, on my GM product car it is in the air intake hose, it is small and has a 2 wire connector to it, just pushes and pulls in and out of the flexible air intake hose.

Posted on Mar 13, 2009

  • 202 Answers

SOURCE: 1995 Toyota Camry - Code 71 - failed emissions tests

replace the EGR switching valve and have the machanic clear the engine check light. I think it should help



Posted on Mar 31, 2009

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1 Answer

High nox on emmission but no engine codes


Check for a vacuum leak by doing a smoke test and see where the smoke is pulled into the vacuum line.

May 25, 2017 | 2002 Mazda Tribute

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94 22re misses at idle


John, did you change the spark plugs?

Nov 16, 2013 | 1994 Toyota Pickup

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I have a scan tool that says my egr valve system not ready on my Ford f150 5.4 and my catylist reads not ready how can I fix this problem


ABout EGR codes, there are alot choive to look or diagnostic... are you chec or replace the vacuum lines as well? If there is a leak, the DPFE will read incorrectly.

Did you reset the PCM or disconnect the battery after the repair? Assuming all fuses are good, the P1401 indicates a possible wiring fault. Check the connector. Is it clean? Is it pushed in all the way? Are the wires in good condition?

Since the DPFE has been replaced, likely there is a restriction in the EGR line some where. This could also be a bad EGR valve. But first ensure that the EGR valve vacuum line is attached and leak free.

If no problem found, then the EGR passageways in the throttle body should be cleaned. Carbon will build up and block the EGR flow.

If still no problem found, consider replacing the EGR valve.

Keep in mind this information from Ford Service CD...

P0401 - EGR Flow Insufficient Detected
The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum.
Vacuum supply
EGR valve stuck closed
EGR valve leaks vacuum
EGR flow path restricted
EGRVR circuit shorted to PWR
VREF open to D.P.F. EGR sensor
D.P.F. EGR sensor downstream hose off or plugged
EGRVR circuit open to PCM
VPWR open to EGRVR solenoid
D.P.F. EGR sensor hoses both off
D.P.F. EGR sensor hoses reversed
Damaged EGR orifice tube
Damaged EGRVR solenoid
Damaged PCM

Perform KOER self-test and look for DTC P1408 as an indication of a hard fault. If P1408 is not present, look for contamination, restrictions, leaks, and intermittents

P1401 - DPF EGR Sensor Circuit High Voltage Detected
The EGR monitor checks the DPF EGR sensor signal to the PCM for high voltage. The test fails when the average voltage to the PCM goes to a voltage greater than the maximum calibrated value.
DPF EGR circuit open
VREF short to PWR
Damaged DPF EGR sensor
DPFEGR circuit short to PWR
SIG RTN circuit open
Damaged PCM

A DPF EGR PID reading greater than 4.5 volts with the key ON and engine OFF or running, indicates a hard fault.


Hope this helps (remember to rate and send us your comments about this answer).

May 22, 2011 | 2001 Ford F150 Styleside SuperCrew

1 Answer

Check engine code#401


Your 401 code relates to the EGR system, vacuum hose leaks are more common for code setting. Also check vacuum modulator as they are known to faile more often than egr valve. If all check out o.k. and there are no exhaust leaks, suspect e.c.m. (computer) problem.
You may just want to check your gas cap also and make sure there is not any air coming through or it will throw off the sensor. Just a quick cheap check. (You may need to change it)

Feb 17, 2011 | 1994 Toyota Corolla

1 Answer

FAILED EMISSIONS TEST P0401&P0420 CHECK ENGINE LIGHT RESETED MANY TIMES WHEN CUT OFF ENGINE LIGHT COMES BACK ON AFTER 5-6 MILES. I HAVE REPLACED EGR VALVE .STILL WA\ONT PASS INSPECTION. WHATS NEXT?


P0401 indicates that the Exhaust Gas Recirculation Flow Insufficient Detected. This can be because EGR is faulty . As you have replaced this then the problem must be with the vacuum line . EGR valve vacuum line which can be broken or blocked. The vacumn ine must bbe checked for leaks or any blocks using an vacumn pump connected the line.

P0420 indicates that the down stream oxygen sensor reading is not steady and it is connected with the code P0401.

Jan 05, 2011 | 2001 Toyota Camry

1 Answer

Code p401..egr .replaced egr still light comes on.


your code relates to the egr system, vacuum hose leaks are more common for code setting. Also check vacuum modulator as they are known to faile more often than egr valve. If all check out o.k. and there are no exhaust leaks, suspect e.c.m. problem.

Jan 30, 2010 | 2000 Toyota Camry Solara

2 Answers

How many different problems can the p0401 code be on a 2001 mitsubishi mirage 1.8 litre


In short,it's all cause by carbon built up.

EGR valve can fail after 100,000 miles.

===
Check for

vacuum leaks on intake manifold,

the air tube between the air filter.

intake manifold vacuum hose.

===
clean throttle plate with Berryman carburator cleaner

SEE sample picture HERE
===

Also remove carbon built up behind the EGR valve and the EGR passage tube.

===

Vacuum leak WILL offset the intended 14.7 to 1 air fuel ratio.

More un-metered air (leaks) will lean out the fuel mixture.

Use small amount of Berryman carb clearer at potential air leak area will help you identify trouble spot.

At idle,just spray and listen for the RPM surge.

The in-rush of carb clearer will increase the RPM on the motor.

Record the problem spot(s) and address it later.

===

EGR carbon built up require 2+ hours to clean from start to finish.

You will need a new EGR base gasket before your start.

Locate and remove the EGR valve after the vehicle is cool down.

Carefully record the connector and vacuum line (for older vehicle) location by drawing an easily to follow diagram.

Remove the EGR valve.

Inspect the location of the carbon built-up inside the valve and the EGR passage tube.

SOAK these areas with WD-40 spary.

You will need a small screwdriver,cloth hanger and lot of newspaper and time to get this cleaning done right.

RE-SOAK the carbon and let it sit for over-night will also help.

One the last round,pass a shop vacuum of the EGR valve and the passage pipe.

Install the new EGR gasket and connectors.

Allow the vehicle to warm up outdoor to burn up any remaining WD-40.


Take it for a test drive.


Please rate my answer if it's useful to you.


Cheers,

Mustgo

Nov 04, 2009 | 2001 Mitsubishi Mirage

2 Answers

Engine light on


Check for

vacuum leaks on intake manifold,

the air tube between the air filter.

intake manifold vacuum hose.

===
clean throttle plate with Berryman carburator cleaner

SEE sample picture HERE
===

Also remove carbon built up behind the EGR valve and the EGR passage tube.

===

Vacuum leak WILL offset the intended 14.7 to 1 air fuel ratio.

More un-metered air (leaks) will lean out the fuel mixture.

Use small amount of Berryman carb clearer at potential air leak area will help you identify trouble spot.

At idle,just spray and listen for the RPM surge.

The in-rush of carb clearer will increase the RPM on the motor.

Record the problem spot(s) and address it later.

===

EGR carbon built up require 2+ hours to clean from start to finish.

You will need a new EGR base gasket before your start.

Locate and remove the EGR valve after the vehicle is cool down.

Carefully record the connector and vacuum line (for older vehicle) location by drawing an easily to follow diagram.

Remove the EGR valve.

Inspect the location of the carbon built-up inside the valve and the EGR passage tube.

SOAK these areas with WD-40 spary.

You will need a small screwdriver,cloth hanger and lot of newspaper and time to get this cleaning done right.

RE-SOAK the carbon and let it sit for over-night will also help.

One the last round,pass a shop vacuum of the EGR valve and the passage pipe.

Install the new EGR gasket and connectors.

Allow the vehicle to warm up outdoor to burn up any remaining WD-40.


Take it for a test drive.


Please rate my answer if it's useful to you.


Cheers,

Mustgo

Sep 15, 2009 | 1997 Toyota Land Cruiser

1 Answer

Po401 and po420 (95 toyota previa Van super charged engine)


Check for air leak into system after MAF.

Check for

vacuum leaks on intake manifold,

the air tube between the air filter.

intake manifold vacuum hose.

===
clean throttle plate with Berryman carburator cleaner

SEE sample picture HERE
===


Check for loose or no connected vacuum hose(s).


Take it for a test drive.


Please rate my answer if it's useful to you.


Cheers,

Mustgo

Sep 05, 2009 | 2001 Toyota Tacoma

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