Hello,

I have a 2008 Dodge Grand Caravan that is throwing p0108 and p0406. Several lights show up on the dash including CEL, ETC(lightning bolt), traction control and others (attached photo).

The problem happened as I was driving and at first was just the lights but then later turned into the car going into limp mode.

I have tried the following:

1. Replaced EGR valve
2. Replaced ETC (Electronic Throttle Control)
3. Replaced MAP sensor
4. Replaced PCV valve
5. Ran SeaFoam through it twice

 

What engine size (3.3, 3.8, 4.0) and transmission (4 or 6 speed) does it have? They’re basically the same but it makes a difference for which wiring diagram I need to look at.

For all those lights to come on suddenly like that at the same time sounds like an issue with a primary power, ground or possibly the data circuit.

Have you checked any fuses? What’s the condition of the battery and cables (age/corrosion build up)?

Is it stuck in limp mode or are you able to drive it again? When idling, is it running rough? If you have a vacuum gauge, what is the reading at idle; or if it won’t idle, what’s the reading while cranking?

 

First off, thank you for your reply!

Engine size: 3.8L.
Transmission size: unknown. How can I find this out? Bolt pattern? Or is there an easier way?

I've been leaning towards an electrical problem but I was hoping that was not the case

Fuses are ok. Battery is older (5-6 years) but no corrosion. I'll take it to get it tested and report back.

It will go into limp mode on and off. A restart will usually clear it for a few minutes.

It is idling fine. I'll have to get a vacuum gauge and check the reading. What's the best place to attach it to?

 

Nevermind on the transmission- I found out the grand caravans with the 3.8 were only equipped with the 6 speed.

Is that a scanner or a code reader you have? Diagnosis will be easier if you can read live data as opposed to just the freeze frame data captured by the code. The pics you posted of the data readings don’t make sense (more details on that later).

The vacuum gauge can be hooked up to any port on the intake manifold as long as it’s “behind” the throttle body (in terms of air flow). The brake booster line is the easiest but sometimes adapting the line for a vac gauge can get tricky.

 

It is a scanner. The screenshots were from the live data view.

I'm out of town this weekend and part of next week but I will have the battery checked as well as get my vacuum gauge reading as soon as I can and report back. Thank you so much for your help!

 

Ok, whenever you’re ready to continue diagnosis, here’s some more info. At this point, don’t worry about the vacuum reading at idle - the point was to verify the amount of vacuum the engine was generating but I don’t think it’s necessary at this point.

What I meant by the data readings not making sense is primarily the MAP/BARO readings - the scanner states both these readings are measured as in-Hg which is typical for measuring vacuum. The problem with the readings is they’re both much higher than they should be - even a brand new engine is only going to create about 20 in-Hg of vacuum, so to see readings of 33.1 (photo 3) and 27.2 (photo 6) indicates a faulty sensor or a problem with the circuit supply voltage.

Since you already replaced the sensor, checking the wiring is the next step. Unplug the MAP sensor and use a meter to check voltages as listed below.

With the key on, engine off:

Pin 1 & 2 shouldn’t have any/very little voltage on them (less than 0.2 volts)
Pin 3 should have about 5 volts on it +/- 0.2 volts

If the voltage on any of these wires is above those specs, the next step is to unplug the PCM and check them again. If there’s still high voltage present, there’s a short to voltage in the harness. If not, the PCM is most likely at fault but there would be a few more checks to make first before condemning it which I can explain if needed.

 

In another thread (EGR valve P0404), it was reported that corrosion in two connectors are causing various problems on the 3.3L & 3.8L vans:
You may want to check those connectors for corrosion.

The two connectors are located just behind the alternator, both are ten pin connectors.

Here are pictures of the connectors:


Close up:


The circuits that run thru the connectors are as follows:

Black:
EGR SIGNAL
MAP SIGNAL
ECT SIGNAL
EGR CONTROL
INJECTOR 2 CONTROL
INJECTOR 4 CONTROL
COIL 1 CONTROL
COIL 2 CONTROL
COIL 3 CONTROL
GROUND

and

Brown:
FUSED ASD OUTPUT
INJECTOR 1 CONTROL
INJECTOR 3 CONTROL
INJECTOR 5 CONTROL
INJECTOR 6 CONTROL
SENSOR GROUND
5 VOLT SUPPLY

 

Well. I think we found the problem. Thanks for the tip on checking the connectors. The black one has some bad corrosio/melting issues. I tried to find a replacement connector but can't seem to find one without knowing the name of it. Any ideas?

Looks like it may be a pain to change out due to the location.

 

Just thought I would update everyone. Tried to clean the connectors up but couldn't get rid of the corrosion. Got some connectors off a donor van via the local junkyard. Got them soldered in. This got rid of the p0108 code. Still had the p0406 code. Decided to replace the EGR valve for a third time. That got rid of the last code! Thanks again for everyone's help!