Egr circuit malf/electrical test

Last Edited By Krjb Donovan
Last Updated: Mar 11, 2014 07:47 PM GMT


QUESTION: Hello Roland. I am working on a 2001 Chrysler LHS 3.5 liter H.O. with 170,ooo+ miles for my Grandaughters school teacher. Here is what I have: Car will hesitate on acceleration (SEVERE), and will not go over 10-12 mph,mis-fire at idle(slight, but noticeable). and will almost die on deceleration (in park,or in gear). I found 1 ignition coil burned-thru on passenger side of engine, and all 3 plugs fuel fouled on passenger side of engine ( but not driver side ). Replaced ALL plugs, 1 coil. **NO SES LIGHT ON DURING THIS TIME** ( but comes on at start up), and I hear what sounds like a whistling sound on acceleration. ANY help would be GREATLY appreciated!! I will send photos, if needed. Thank you in advance, Frank

ANSWER: Hi Frank, Even though the check engine light is only coming on when you start it that does not mean that the engine controller has not noticed some problem(s) and logged them in memory. Try turning the ignition switch "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window to see if the mileage reading changes to show instead a 4-digit number(s) preceded by a P. Let me know what happens. If nothing changes at the odometer then get a free code readout at a nationwide auto parts store such as Autozone. Or an independent shop will usually charge $40 or less for a readout. You would do well to disconnect the battery for a minute now to erase all old codes, then drive it for a while to set any fresh codes and then seek the readout by the key and/or by the plug-in reader at a store or shop. The whistling sound may well be an intake manifold air leak which you may be able to localize by means of a spray can of starter fluid while idling, putting very SMALL sprits of fluid around the edges of the manifold and notice any change in the idle with each squirt. But the fault codes are the most helpful to have as well. The description of how it is running makes me believe that there is a very lean mixture due to an air leak around the manifold gasket, or another possibility is that the exhaust gas recirculation valve is sticking ajar which also causeds a too lean mixture at idle, deceleration, and acceleration. Thanks for the rating and nomination, Frank. It would be good to also check all the vacuum hoses connected to the intake manifold to see if you can find a loose or disconnect at both ends of each hose or a damaged hose. Use the vacuum diagram on the underside of the hood as a guide. Roland

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QUESTION: Hello again, Roland. I have follwed your direction, no vaccume lines are worn, loose or broken, no leaks for short time that the engine will stay running. I removed EGR Valve, got connector diagram from local library ( chilton online service found there, but no pin-point diag offerd ), and applied battery power to EGR Solenoid Power pin as shown, applied ground to Sensor Ground pin as shown, and applied power from battery to EGR Solenoid Control pin as shown, and I have no movement/ activation of valve itself. I have verified power and ground with key on, engine off at EGR harness connector pins as shown. I feel the valve has failed, would like second opinion before ordering part. Also, researched valve failure,seems pretty common? Thanks again for the help! Frank

ANSWER: HI Frank, Have you checked out the movement of the valve/valve stem mechanically, if accessible to you? It may just be gummed up. The problem would be if it was gummed up ajar so if you can verify that it moves and closes tightly then you wouldn't have to buy a new one. The manual I have shows a 6-pin plug, and if you apply 12v to pin 6 (connected to the orange/green wire) and ground pin 4 (connected to gray/yellow wire of plug) then the valve/valve stem should move and return when you take off the power. Nice going so far. Feel free to do another rate/nominate if you are so-moved. Roland

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QUESTION: Hello Roland, I would like to know what "disconnect the load " means in the short to ground test? I have checked pin 40 (grey/yellow) wire at the ECM by connecting the red wire lead to the battery post, turned the volt multimeter to 12v setting, and front probed the ECM connetor at pin 40 with the black wire lead, and have 11.50 volts with the key off, and with the key on, 11.50 volts. I disconnected the EGR valve connector, and got .345v. I follwed the instructions for short to ground test, but I am not sure of the "disconnect the load ", as I said. Thanks again, Frank


Hi Frank, I couldn't find where I said to 'disconnect the load' so am not certain what to say. Basically, pin 6 at the egr plug always has 12v on it. Similarly, if the ecm 1-40 pin plug is disconnected the pin 40 of that pcm plug will show 12v always UNLESS the wire from pin 4 of the egr solenoid to pin 40 of the ecm plug were shorted to ground in which case it would instead show 0v or something very close to it. The last test would be to see what pin 40 of the ecm's socket is showing (and you would measure that at pin 4 of the egr plug when disconnected from the egr). When the key is on run it should read 12v or possibly no volts at all and if the latter were the case you would want to then switch to the ohm scale and show that it was not shorted to ground (near zero ohms, and ideally near infinite ohms instead). We are trying to verify that the egr is not being activated when the key is in the run position by there being either 12v or a disconnect at pin 40 rather than a ground at pin 40 of the ecm which would then open the valve and cause hard starting/poor idling/poor low rpm function. Roland


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