P0403 on 1997 Dodge Intrepid

I have trouble code P0403 - EGR FLOW CIRCUIT MALFUNCTION on a 1997 Dodge Intrepid, 3.5L engine. I replaced the EGR valve. The new valve came in 2 parts, it included a differential pressure sensor attached with hoses.

The engine light is on most of the time, but it goes out some times. One of the times it was out, I took it down and it passed a smog inspection, but the light came on again while driving home. The engine light seemed to be doing the same thing, i.e., going on and off both before and after I replaced the EGR valve. It didn't seem to make a difference in that regard.

I don't have a gauge to check the vacuum but I disconnected the hose going to the differential pressure sensor while the engine was running and there seems to be plenty of vacuum there.

There is a stainless steel pipe that comes up from the EGR valve and connects to both sides of the intake manifold. Could it be carbon build up in this tube?

The EGR valve problem doesn't seem to be affecting the way the engine runs - the engine runs very smoothly.

Do you know what the trouble could be?

Thanks!
Denny

The code is for the EGR SOLENOID circuit. SO it most likely an EGR solenoid or the wiring to it.
As for checking the EGR solenoid
1. Check the resistance of the Exhaust Gas Recirculation (EGR) solenoid. 25-35 ohms at room temperature.

2. Check for Batt. voltage on the Light Green/Black wire.

3. Check for opens or shorts inthe Gray/Yellow wire at pin 40 at the PCM

It is possible that the tube would plug on those but it is common, more common is a broken wire to the egr solenoid! It's only a 2 wire connector so just trace the circuit and find the break!

Thanks, Darkrooms, for a very detailed procedure to check, and thanks, jeff, for letting me know of the common cause for this.

Do either of you know if there is a place online where I can take a look at a diagram of this part of my engine to tell me where this solenoid is?

Just follow the vacuum line fromyour EGR valve until you find a black plastic disc shaped object with a cylindrical attachment. The cylinder is your EGR solenoid, but it's a unit joined with a transducer(disc shaped thing) I believe they are mounted at or near the EGR valve.
Pardon the colloquial speech.

I think this describes the thing I thought was a differential pressure sensor, which was part of the new EGR valve I replaced. As I recall, there were 2 wires going to it, connected via a connector. I tried to make sure they were making good connections, and I thought they were, but maybe not? I tried jiggling around the wires while it was running, but it didn't seem to make a difference. I don't recall the wire colors. I will use the step-by-step procedure you provided in your first post to check this.

Thanks!
Denny

Hey, Darkrooms, one more question:



What is the PCM and where can I check this?

TIA!

Uh, I re read my post and realized I made an error. I'm looking at a diagram now during my lunch break and I'll post hopefully in a few minutes with the right procedure.

yeah wiggling it won't cause any kind of miss at idle becuase it shouldn't be open at idle and if it is open the pintle is seized and wiggling the wires won't unseize it! Very rarely is the pcm ever the issue with these codes on that car! Wiring is probably the issue on this car, the wires tend to break alot around the bell housing bolts!

To check Egr solenoid operation(since you said it was replaced with the EGR valve) unplug the connector to the solenoid. Should be only 2 wires.
One wire will be Lt. green with a black tracer. This one should have 12 Volts with the key on and engine off. Use a voltmeter or test light to check.
If you have voltage there, then move on to the other wire. The other wire is Grey with a Yellow tracer. This is the PCM's(computer's) ground circuit. The PCM grounds this wire to operate the solenoid. If you have voltage then suspect an open in this wire, the ground circuit.

If you do not have voltage on the first wire(the feed) then check fuse #20(use your manual) it should be a 10 amp fuse. This fuse feeds that first circuit(light green/black)

Post back with what voltages you have and what you do not have and I or someone will try to help walk you through the reasoning.

Hey, thanks to both of you, Darkrooms & jeff! This is the best help I've ever received! Most of the time I ask at the parts counter and they point me in the right direction, but this forum is the greatest. I will post back with results, but it may be a day or 2.

Thanks!
-Denny

Well, glad to help. It's nice to talk to an appreciative customer once in a while. Compton is a chrysler tech so he's very familiar with them and I work at an independent shop. There are so many malcontents that post their vehicle problems(see recently locked thread) and get angry when they aren't given , as Comp puts it, a "magic bullet" to fix it immediately. So, thanks!

Well, the help sure is appreciated, believe me!

I am a computer programmer by profession, but I'm pretty technically minded. I used to be an electronic technician, so I understand wiring and reading schematics and such. To save money, I like to do my own mechanic work unless it's a huge job or something that would take too much time. I am what you might call a "Saturday" mechanic. I wish I would have found this forum a long time ago -- it would have saved me a bunch of time trying to figure things out myself.

Thanks to the both of you for all the help! Darkroom, I said you were a true Jedi in another post, but I'd like to change that assessment -- you are a true Jedi MASTER!

-Denny

From ground (intake manifold) there is 12V on the green/black wire and 20mV (0.02V) on the grey/yellow wire. 20mV is close to ground - do you suspect this is open?

Okay, you have voltage. But the negative reading can't be trusted because there's capacitors in the PCM and stuff like that and sometimes multiple circuits use the same driver. We don't know if the EGR solenoid circuit is grounded with a reading of 20 mV it sounds like it is(chryslers allow 50 mV voltage drop maximum).

So, the next thing to do is verify the ground circuit is okay(it's possible for a circuit to test okay without a load on it, but when a load is applied to the circuit, problems are revealed. For example a frayed wire with one strand intact can test fine with no load, but with load, the amp draw is too great to pass over one strand and therefore, bottlenecks, creating heat, melting, etc). If you have access to a scan tool, this vehicle supports an ATM test. Basically it activates the solenoid on and off for 5 minutes. Normally I'd run this test to see if the circuitry was okay or not. You can wiggle the connector on the right shock tower while running this test and see if the solenoid clicking is interrupted. If it is- there's a poor connection in that connector. If the solenoid clicks for 5 minutes then the circuit's wiring is okay and not the problem(unless it's an intermittent short)

The only other thing you can do is to remove the #40 wire from the PCM's connector and manually check if the circuit is okay. With the EGR solenoid connector plugged in and the the PCM's connector plugged in and the ground wire removed from the PCM's connector and NOT plugged in, Check for voltage at the wire. If there's no voltage, then youknow that voltageisn't traveling through the EGR sol. windings, down the ground wire and into your voltmeter, and therefore it is open somewhere. You could also ground it and verify the solenoid clicks, which means the circuit is good. (Key on engine off of course)

There's a problem somewhere on the EGR solenoid driver circuit, because of the code definition. It can really only be two things

1. The Egr control circuit is open or shorted
2. Failed PCM

Always double check everything when diagnosing PCMs.
HOpe this helps
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