you guys have been very helpful in getting my 2003 back in good shape and I have another issue to ask help on. Today my 2003, V6 Dak began running very rough at all speeds. When I get it to about 55 mph and it downshifts and the rpm's drop it runs very rough and the check engine light flashes. If I speed up to above 65 or take my foot of the gas the flashing stops. The engine light now stays on. I'm limping it home from a trip to Georgia. Any ideas?

 

You need to find out why the CEL is on. When a CEL is flashing it is not good to keep driving, because a flashing CEL indicates a serious engine problem that could lead to engine failure. A CEL that is lit up steady indicates an emissions system problem and you could most likely still drive it but you might get worse MPG or maybe less power.

You can stop by Auto Zone or Advance and they should read be able to the code for you for free. Or you can turn your ignition key from "Off" to "On/Run" and back to "Off" 3 times, on the 3rd time leave the key in the "On/Run" position and any trouble codes you have will display in the odometer. If there is more than one code stored it will show all of them in succession and then it will say "P Done" at the end. Write down the codes and check the trouble code lists in the FAQ section at the top of the 2nd Gen page here or post back here for more info if we can help. The codes will tell you what could be wrong and give you an idea of how to fix the truck.

Jimmy

 

I did what you suggested and get

P 0141 - 02 Sensor

P 0304 - Misfire on cylinder #4

P 0138 - O2 Sensor shorted to voltage.

Any suggestions on how to proceed?

 

P0141 indicates a failed O2 sensor heater circuit.
P0138 indicates the failed O2 sensor is Bank 1, Sensor 2. This is the O2 sensor after the catalytic convertor on the driver's side exhaust pipe.
P0304 indicates a misfire in #4 cylinder. That is the middle cylinder on the passenger's side of the truck.

With the truck running rough like it is, you may want to replace both the Auto Shut Down Relay and the O2 sensor heater relay. Both relays are located in the Power Distribution Center under the hood. There should be a chart on the bottom of the cover to show where they are located. Relays do not normally fail on their own so I am wondering if you drove through any heavy rain or standing water on your trip and the relays got wet? If and when a relay ever does fail it is usually due to moisture, corrosion or physical damage. If your relays look OK you can check them with a volt-ohm meter, or you can just replace them anyway. To check with a meter, remove the relay, set the meter to continuity and you should have continuity between terminals 30 and 87a. 87a is the terminal in the middle. Apply ground to terminal 85, and fused 12 volt power to terminal 86. These 2 terminals provide ground and power to the coil in the relay. When you do that you should feel a slight "click" in the relay as the coil is energized. With the relay energized, apply 12 volts to terminal 87. When you do that there should be no voltage on 87a and there should be 12 volts output on terminal 30. De-energize the relay and the 12 volts should be present on 87a and there should be no voltage on 30. That is how relays work, they are a switch operated by an electromagnetic coil. You may not be able to test that right now since you are trying to limp home so maybe you could just replace the relays anyway.

The O2 relay supplies voltage to both downstream O2 sensors. The ASD relay provides voltage to both upstream O2's. You might just have a bad relay but if you replace them and still have the problem there might be a wiring problem or moisture/corrosion in the relay cavities on the Power Distribution Center, or there might be an internal problem with your PCM. You also need to replace the faulty O2 sensor. This part sounds to me like there is a voltage problem with the O2's and that could be why the CEL is on steady.

The misfire is another problem. It could be a fouled spark plug in that cyclinder, you could have a bad plug wire for that plug or it could be a bad distributor cap and/or rotor button. Any or all of these problems can and will cause the engine to run real rough or not at all. How long has it been since your last tune up?

You could stop at a parts store and pick up new spark plugs, a wire set, cap and rotor and replace just that one plug, wire and also replace the cap and rotor. You could do that much in the parking lot at the parts store and maybe it will be enough to get you home. With O2 sensor problems the truck could make it back home but you may have power loss and probably will use a lot more gas than normal.

Depending on how far from home you are and if you have towing coverage on your car insurance or if you have AAA it might be better to try to tow the truck home instead of fixing it on the side of the road.

This is all just my 2 cents on the problems. Others here will probably have better info for you. Hope this helps you get it back home.

Jimmy

 

Jimmy, thanks so much for your help. I drove through torrential rain on this trip. I am going to go replace the wires, cap, and rotor and then attack the o2 sensor issue. I'll let you know how it all turns out!

- Mark -

 

Some additional info. I haven't yet done anything - change spark plug wires/cap/rotor. Today I drove to the store and it didn't seem to run as rough as it did yesterday but I could smell gas. I intend on changing the wires/cap/rotor tomorrow and see what happens. Maybe the spark plugs as well.

- Mark -

 

The gas smell could be from the exhaust, the bad O2 could be causing the truck to run too rich. Hopefully a new O2 will fix it. You can get O2 sensors for a good price at www.ngk.com. NGK is the supplier for the OE sensor for Dodge, they cost about $62.00 each when you order online and they have very fast shipping. You can get the OEM part at the dealer too but who knows how much they cost. I have heard and read that the Bosch sensors they sell at parts stores just don't work very well with the Magnum engines. I replaced both of my upstream O2's at 85,000 miles and ordered the parts from NGK and have not had any trouble with them at all.

Maybe all you need is a new O2 sensor and a good tune-up. After that maybe stop by the parts store and get them to clear the trouble codes out of the PCM, or you can turn off the CEL yourself by disconnecting the negative battery cable and holding the ignition key in the start position for 20 seconds. That will clear the CEL but the trouble code remains stored in memory in the PCM. Maybe see how the truck runs then and see if the CEL comes back on. I would think if the CEL stayed out for 2 or 3 days the truck would be fine.

I have seen a few of us here lately with the misfire codes. Please let us know how it all turns out.

Jimmy

 

I cleared out all the codes as suggested. After changing the spark plug wires the truck runs GREAT - no misfires. I haven't changed the cap and rotor as yet but since I got them I will put them on latter. I've not done anything with the o2 sensor but my Dak is running really smooth with good pickup!

- Mark -