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2slo 01-01-2012 06:09 PM

EGR Code P0405
 
Hi all,
I am working on a new-to-me 2000 SC2 with a 1.9L DOHC engine. The check engine light is on and my scanner reveals P0405 code.
I have read numerous posts on this site about cleaning the EGR valve and ports and have done so several times only to have the code reset within a moment or so. In one post in particular the pin-out for the valve was listed. The post stated that the valve receives 2 voltage sources: 1) a 5v source for the sensor position and 2) a 12v source for the servo motor that moves the pintle. When I remove the connector from the EGR valve and probe the connector I read 5v on the 5v source. Using a 12v test light from the 5v source to ground causes the light to glow. With the connector attached to the valve the 5v remains. So far so good.
When I probe the connector for 12v I only read 8.5v. A test light hooked from the 12v supply wire to ground fails to light and the 8.5v goes to 0v. Further, if I reconnect the wire to the EGR valve the 8.5v goes to 0v. I checked for a short from the 12v pin on the EGR valve to ground and none exists.
From where is this 12v derived? Has anyone else experienced this issue? Where can I find a wiring diagram to aid in trouble shooting this problem?

fdryer 01-01-2012 07:05 PM

Re: EGR Code P0405
 
1 Attachment(s)
From the service manual;

[I]The exhaust gas recirculation (EGR) valve consists of a pintle valve which moves by the use of an internal solenoid and an internal position sensor (potentiometer) used to determine pintle valve position. The powertrain control module (PCM) controls the solenoid by supplying it ignition voltage whenever exhaust gas needs to be recirculated into the intake manifold. The PCM monitors the EGR solenoid and position sensor circuits for correct voltage levels at certain times. DTC P0405 sets when the EGR sensor signal voltage is below the calibrated voltage value. [/I]

Be sure you have the correct information from known good sources otherwise going on assumptions can result in confusion.

The pintle valve motor only powers up [U]momentarily[/U] when the pintle valve is needed to be positioned so you're not likely to see 12v unless you're willing to conjure up a set up to monitor the control voltages as the egr valve operates when necessary - that's only going to occur when the engine's under load and accelerating in normal driving (not while idling/revving in place). There's also the possibility of damage to the position sensor that provides feedback signaling so the pcm knows where the pintle valve is.

OldNuc 01-01-2012 07:06 PM

Re: EGR Code P0405
 
The 12v is from the PCM(ground) and battery. How have you been cleaning out the ports? The 12v is not your problem most likely. Pin C to Pin B voltage must be greater than 0.2v. To test this connect EGR and start car then probe the c and b wires with a pair of straight pins inserted through the insulation. Back probing is an excellent method to fail the connector so skip that one unless you know how that connector is constructed. You should see grater than 0.2v and if not then the PCM grounds become suspect. If you have an aftermarket EGR suspect a defective valve.



[QUOTE=2slo;1827438]Hi all,
I am working on a new-to-me 2000 SC2 with a 1.9L DOHC engine. The check engine light is on and my scanner reveals P0405 code.
I have read numerous posts on this site about cleaning the EGR valve and ports and have done so several times only to have the code reset within a moment or so. In one post in particular the pin-out for the valve was listed. The post stated that the valve receives 2 voltage sources: 1) a 5v source for the sensor position and 2) a 12v source for the servo motor that moves the pintle. When I remove the connector from the EGR valve and probe the connector I read 5v on the 5v source. Using a 12v test light from the 5v source to ground causes the light to glow. With the connector attached to the valve the 5v remains. So far so good.
When I probe the connector for 12v I only read 8.5v. A test light hooked from the 12v supply wire to ground fails to light and the 8.5v goes to 0v. Further, if I reconnect the wire to the EGR valve the 8.5v goes to 0v. I checked for a short from the 12v pin on the EGR valve to ground and none exists.
From where is this 12v derived? Has anyone else experienced this issue? Where can I find a wiring diagram to aid in trouble shooting this problem?[/QUOTE]


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