OBD-II Trouble Code: P0401 on 1996 Camry 4 cylineder
in [Toyota]
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From: SMS on 4 Sep 2009 17:41 Just got the P0401 code on a 1996 Camry. I cleared it, but it came back the next day. I know what it says "Insufficient EGR Flow" but what is the procedure for finding the offending part? The vehicle has 130,000 miles and has never had an EGR valve replacement.
From: Hachiroku ハチロク on 4 Sep 2009 20:15 On Fri, 04 Sep 2009 14:41:28 -0700, SMS wrote: > Just got the P0401 code on a 1996 Camry. I cleared it, but it came back > the next day. > > I know what it says "Insufficient EGR Flow" but what is the procedure > for finding the offending part? The vehicle has 130,000 miles and has > never had an EGR valve replacement. You can remove the EGR and check it. This is for a Supra, but the method should be the same: http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=EC&P=12 Note, however, that code 401 also covers other things. My '95 Tercel was throwing a 401, local Toyota dealer checked the EGR, I replaced the O2 sensors (also covered under 401, IIRC) and it turned out to be a bad vacuum line!
From: Ray O on 5 Sep 2009 01:44 "SMS" <scharf.steven(a)geemail.com> wrote in message news:4aa1893b$0$1586$742ec2ed(a)news.sonic.net... > Just got the P0401 code on a 1996 Camry. I cleared it, but it came back > the next day. > > I know what it says "Insufficient EGR Flow" but what is the procedure for > finding the offending part? The vehicle has 130,000 miles and has never > had an EGR valve replacement. I've been posting on another thread for the same problem. If you have a Mighty-Vac hand held vacuum pump, apply vacuum directly to the EGR valve while the engine is idling. If the EGR is opening properly and the valve and tube leading from the valve to the intake manifold is not clogged, the engine should start to idle roughly and want to stall when the EGR valve is opened. If the engine idles normally or almost normally when you apply vacuum to the EGR valve, the valve is stuck, clogged, and/or the metal tube between the EGR valve and intake manifold is clogged. You can try removing the valve, and if it is caked with carbon inside, you can try digging out the carbon inside the valve and tube with a screwdriver or awl or just replace the valve. If the engine does start to idle poorly or stalls when the EGR valve is opened, then check the sensor on the output side of the EGR valve. The sensor is either an EGR gas temp sensor which should sense the rise in temperature that results when the exhaust gas flows from the EGR valve, or the sensor is an EGR position sensor, which senses whether or not the EGR valve is opening. Either way, you can put a volt meter on the sensor terminals and you should sense a change in voltage when the valve opens. If there is no change in voltage, sensor is bad. If there is a change in voltage, then it is on to the next steps. If the engine idles poorly when the EGR valve is opened, signifying that the EGR valve is operating properly, and the sensor is good, check the EGR modulator (google "Toyota EGR P Q R" to find instructions on checking the EGR modulator or look for the thread where I posted instructions recently. Don't worry if the instructions are for a different model or engine - the check is the same. -- Ray O (correct punctuation to reply)
From: SMS on 5 Sep 2009 21:31 Ray O wrote: > "SMS" <scharf.steven(a)geemail.com> wrote in message > news:4aa1893b$0$1586$742ec2ed(a)news.sonic.net... >> Just got the P0401 code on a 1996 Camry. I cleared it, but it came back >> the next day. >> >> I know what it says "Insufficient EGR Flow" but what is the procedure for >> finding the offending part? The vehicle has 130,000 miles and has never >> had an EGR valve replacement. > > I've been posting on another thread for the same problem. > > If you have a Mighty-Vac hand held vacuum pump, apply vacuum directly to the > EGR valve while the engine is idling. If the EGR is opening properly and > the valve and tube leading from the valve to the intake manifold is not > clogged, the engine should start to idle roughly and want to stall when the > EGR valve is opened. If the engine idles normally or almost normally when > you apply vacuum to the EGR valve, the valve is stuck, clogged, and/or the > metal tube between the EGR valve and intake manifold is clogged. You can > try removing the valve, and if it is caked with carbon inside, you can try > digging out the carbon inside the valve and tube with a screwdriver or awl > or just replace the valve. > > If the engine does start to idle poorly or stalls when the EGR valve is > opened, then check the sensor on the output side of the EGR valve. The > sensor is either an EGR gas temp sensor which should sense the rise in > temperature that results when the exhaust gas flows from the EGR valve, or > the sensor is an EGR position sensor, which senses whether or not the EGR > valve is opening. Either way, you can put a volt meter on the sensor > terminals and you should sense a change in voltage when the valve opens. If > there is no change in voltage, sensor is bad. If there is a change in > voltage, then it is on to the next steps. > > If the engine idles poorly when the EGR valve is opened, signifying that the > EGR valve is operating properly, and the sensor is good, check the EGR > modulator (google "Toyota EGR P Q R" to find instructions on checking the > EGR modulator or look for the thread where I posted instructions recently. > Don't worry if the instructions are for a different model or engine - the > check is the same. Thanks Ray. I did go out today and buy a Mity-Vac at Pep Boys so I can try this. I cleared the code yesterday and am waiting for it to re-occur. This is the second time I cleared it, the first time it re-occurred in about 10 miles of driving, but now it hasn't happened again yet. Does the fact that it doesn't quickly cause the Check Engine light to come on again give any clues to whether it's the valve or the tube or the modulator?
From: Hachiroku ハチロク on 5 Sep 2009 21:56
On Sat, 05 Sep 2009 18:31:44 -0700, SMS wrote: > Ray O wrote: >> "SMS" <scharf.steven(a)geemail.com> wrote in message >> news:4aa1893b$0$1586$742ec2ed(a)news.sonic.net... >>> Just got the P0401 code on a 1996 Camry. I cleared it, but it came back >>> the next day. >>> >>> I know what it says "Insufficient EGR Flow" but what is the procedure for >>> finding the offending part? The vehicle has 130,000 miles and has never >>> had an EGR valve replacement. >> >> I've been posting on another thread for the same problem. >> >> If you have a Mighty-Vac hand held vacuum pump, apply vacuum directly to the >> EGR valve while the engine is idling. If the EGR is opening properly and >> the valve and tube leading from the valve to the intake manifold is not >> clogged, the engine should start to idle roughly and want to stall when the >> EGR valve is opened. If the engine idles normally or almost normally when >> you apply vacuum to the EGR valve, the valve is stuck, clogged, and/or the >> metal tube between the EGR valve and intake manifold is clogged. You can >> try removing the valve, and if it is caked with carbon inside, you can try >> digging out the carbon inside the valve and tube with a screwdriver or awl >> or just replace the valve. >> >> If the engine does start to idle poorly or stalls when the EGR valve is >> opened, then check the sensor on the output side of the EGR valve. The >> sensor is either an EGR gas temp sensor which should sense the rise in >> temperature that results when the exhaust gas flows from the EGR valve, or >> the sensor is an EGR position sensor, which senses whether or not the EGR >> valve is opening. Either way, you can put a volt meter on the sensor >> terminals and you should sense a change in voltage when the valve opens. If >> there is no change in voltage, sensor is bad. If there is a change in >> voltage, then it is on to the next steps. >> >> If the engine idles poorly when the EGR valve is opened, signifying that the >> EGR valve is operating properly, and the sensor is good, check the EGR >> modulator (google "Toyota EGR P Q R" to find instructions on checking the >> EGR modulator or look for the thread where I posted instructions recently. >> Don't worry if the instructions are for a different model or engine - the >> check is the same. > > Thanks Ray. I did go out today and buy a Mity-Vac at Pep Boys so I can > try this. > > I cleared the code yesterday and am waiting for it to re-occur. This is > the second time I cleared it, the first time it re-occurred in about 10 > miles of driving, but now it hasn't happened again yet. Does the fact > that it doesn't quickly cause the Check Engine light to come on again > give any clues to whether it's the valve or the tube or the modulator? This might be helpful: http://www.carforums.net/showthread.php?t=82330 At the bottom are PDFs from the factory manual. Good luck. |