Tip & How-To about 1996 Toyota Camry

P0401 Error, Insufficient EGR Flow

In my case this was caused by a bad hose from the Throttle Body to the EGR Vacuum Switching Valve. Pictures are taken from the left side of the car except for the picture of the original hose. This is with the 4 cylinder engine. I used a piece of fuel/vacuum line that I had. It fit snugly which made my cost of repair zero.

This is the end of the original hose with the crack plainly visible.

Hose run from the throttle to the VSV

Replacement hose at throttle (far right). This is where it was cracked.

Replacement hose (far right) on the VSV.

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2 Answers

I have p 1121 and a P 0401 codes on my 1998 ford windstar. are these related? what can I check? replaced the mass airflow sensor recently.




P1121 Ford Throttle Position Sensor Inconsistent with Mass Air Flow Sensor
http://engine-codes.com/p0401_ford.html no they are not related !
Are there any cracks in the rubber hose from air cleaner to throttle body ! That could cause the P1121 air entering after mass air flow sensor !
P1121 - Throttle Position (TP) Sensor Inconsistent with MAF Sensor The PCM monitors a vehicle operation rationality check by comparing sensed throttle position to mass air flow readings. If during key ON engine running self-test the comparison of the TP sensor and MAF sensor readings are not consistent with calibrated load values, the test fails and a diagnostic trouble code is stored in continuous memory.
  • Air leak between MAF sensor and throttle body
  • TP sensor not seated properly
  • Damaged TP sensor
  • Damaged MAF sensor
Drive vehicle and exercise throttle and TP sensor in all gears. A TP PID (TP V PID) less than 4.82 % (0.24 volt) with a LOAD PID greater than 55% or a TP V PID greater than 49.05% (2.44 volts) with a LOAD PID less than 30% indicates a hard fault. 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

Mar 09, 2015 | 1998 Ford Windstar

1 Answer

engine vibrates in idle real bad


sound like idle speed low idle you need to remove throttle body clean entire throttle body spray cleaner down throttle body bore if cleaning throttle body dont help the dealership has to check it out.a faulty egr valve could be stuck partially open that will cause rough idle and stalling. replace air filter clean fuel injectors.your fuel system could be too lean caused by clogged fuel injectors or weak fuel pump check fuel pressure and also check all intake vacuum hoses make sure pcv valve working should have suction and make sure its in place and the pcv valve hose not cracked open or damaged.

Nov 16, 2011 | 1994 Chrysler Concorde

3 Answers

i have a 1999 toyota camry 4 cylinder with the check engine light code of p0401 and i replaced the EGR valve and still have a problem, what else may it be?


there is also a vac. switching valve for the egr that also goes bad.to find the valve follow the vac. line that is hooked to the top of the egr to the valve.it is located on the back of the motor up under the intake and is a pain to replace. if you have a hand held vac. pump hook it to the egr valve and pump it up and see if the engine dies if it does i would replace the vac. switching valve.if it does not die then i would start looking for carbon on the inside of the intake on the back side of the throttle body plate.and also carbon will build up at the intake where the egr bolts to it...before i messed with the vac. switch i would look inside of the throttle body behind the throttle plate and see if the passage that goes to the egr valve is stopped up with carbon and you will need a small round mirrow and a flashlight....if the car does not die when you do the vac. pump test it is easier to take the throttle body off to clean and to check....been working on toyota and lexus for 25 yrs and have seen it all so let me know if i can help in any other way..........good luck and if i did my job let me and fixya know and a thumbs up............thanks.......

Jun 21, 2011 | 1999 Toyota Camry

1 Answer

throttle body reinstalled, firebird idles at 3k rpms?


You have a vacuum leak for sure. Look and listen carefully for anything left off, maybe an egr valve or pcv hose, brake booster line?

Apr 14, 2009 | 1988 Pontiac Firebird

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