1997 Toyota Camry P0401 EGR insufficient flow

Tiny
JCANTERGIANI
  • MEMBER
  • 1997 TOYOTA CAMRY
  • 2.2L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 184,000 MILES
I keep getting this code, even though I have now replaced ALL the components in the EGR system: EGR valve, EGR modulator, EGR Vacuum Switching valve (VSV), and all 5 of the EGR vacuum hoses. I used genuine Toyota parts. All ports and pipe are clear. Both EGR gaskets were replaced. I am getting 12 volts at one of the two terminals that connects to the VSV. Don't know what else I can do. I'm having no other codes or problems with the car. Could it be the ECU is bad anyway, even though there are no other issues?
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Friday, July 31st, 2015 AT 8:43 AM

6 Replies

Tiny
HMAC300
  • EXPERT
See pics for causes.
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Friday, July 31st, 2015 AT 9:25 AM
Tiny
JCANTERGIANI
  • MEMBER
Yes, I know all of those tests. THE PARTS ARE ALL NEW GENUINE TOYOTA PARTS. The hose from the intake to the MAP sensor is not leaking, or plugged, and the MAP sensor holds vacuum when applied. I erased the codes and went on the Toyota EGR drive cycle and followed it exactly. It always trips the pending code during the drive cycle and the it becomes a current code on the 2nd drive cycle. The 5 EGR vacuum hoses are routed correctly.
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Friday, July 31st, 2015 AT 10:02 AM
Tiny
HMAC300
  • EXPERT
Did you check the vsv likit said in second pic and test vacuum through it? Is the egr plugged or partially plugged including passageways. It also can be a bad ecm.
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Friday, July 31st, 2015 AT 12:06 PM
Tiny
JCANTERGIANI
  • MEMBER
Yes, I did. All the parts are new Toyota parts anyway. Nothing is plugged up. Is there a way to check using a multimeter to see if the ECU is switching the VSV on/off? I do get 12 volts at one of the terminals on the plug that connects to the VSV. Is the other terminal supposed to get 12 volts at times to "ground side switch" it? I'm not sure how that can be tested. Is there a way to test the ECU first?
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Friday, July 31st, 2015 AT 12:51 PM
Tiny
HMAC300
  • EXPERT
The pink wire on vsv sensor goes to port 7 on pcm so check that for continuity. The other wires tie in to different sensors as you can see in pic. The second pic with violet wire leads to pin 8 on pcm do the same with that. If everything is getting vacuum then I'd have to go with ecm isn't sending power to operate the system which a pro will have to install due to security systems in them. Icannot send the wiring diagram as it's to big so if you want to delve further then you can either buy a manual, rent one from here under manuals for your car and I think they allow you for a week as I'm not sure or see if a library has one for it.
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Friday, July 31st, 2015 AT 3:35 PM
Tiny
JCANTERGIANI
  • MEMBER
It was the ECU. I went to the junkyard and found one for $39. I installed it and the car started and drove fine. After completing the EGR drive cycle, the readiness monitor completed and there is now no more P0401 code. I didn't have any problem with security or anything else with replacing the ECU by myself. Maybe it's newer cars in which that is the case. Anyway, the problem is fixed with a replacement ECU.
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Tuesday, August 4th, 2015 AT 5:46 AM

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