'04 Ram 1500 4.7L with auto shut down activated, would changing the ECM and having it flashed to the same as the ECM with the shut down take care of this no crank no start problem?

the o2 sensors are responsible for part of the fuel management. You need a good auto-electrician.

P0688 (generic) = ECM/PCM Power Relay Sense Circuit /Open
P0688 DODGE - Auto Shutdown Relay Control Circuit Low

Check all the ECM fuses, if the fuses are OK try replacing the ASD (Auto Shut Down) relay.

Read more: http://www.autocodes.com/p0688_dodge.html#ixzz405J7vpq8

Possible causes:

- Weak battery - Low voltage while cranking
- Faulty Engine Control Module (ECM) relay
- Blown ECM fuse
- Faulty ECM
- ECM harness is open or shorted
- ECM circuit poor electrical connection

there is really no way to test crank sensor unless it shuts down and u have a computer that can check it. I found out after changing the crank sensor that was not my problem the ecm is overheating kicking the auto shut off and after it cools a few min it will crank over this is the 3rd ecm I have tried from orielys auto it cost me 150 bucks each time to program it im over it I am going to try to install cooling fan and see if that will help my problem will let you know if it works or not on later post

Please stop replacing parts it costs money!
Go get a timing light to see if you have spark if you do not it is a bad ignition module.
to check your fuel pump connect a fuel pressure guage to the engine fuel injector rail and turn over the engine the pressure should be: 40 to 60 psi.

Could possibly be bad spark plug wires.
May have a bad coil pack also.

check the auto shut down relay,check fuel pump relay and the fuel pump pressure

The only thing that it would most likely be (if not the ignition module, the fuel pump, a faulty fuel pump relay if applicable, or a faulty ignition coil pack but only if one coil pack is used, and if more than one coil pack they would all have to be faulty to shut down the engine) is the ECM/ECC, especially since the vehicle shuts down about every 10 minutes, and that is the classical sign of over-heating electronics that act almost normal until the electrical componet becomes too hot and then begins to malfunction.

The ECM (Engine Control Module) or ECC (Engine Control Computer) for those vehicles were not manufactured very well and were prone to failure, and that is why you can purchase a re-manufactured one for only $85.00-$89.00, and the re-manufactured one will not have the stock defects.

If you do purchase an ECM/ECC and if it has a PROM chip (Programable Removable On-board Memory) that must be installed from your old ECM/ECC be very careful when removing and installing the PROM, and the plastic retainers on either end of the PROM will push back away from the PROM and lift the PROM out of the connector on the circuit board. When installing the PROM be sure that the retainers are pushed back and that when the PROM is pushed down into the connector that the retainers lock in the PROM. Not all vehicles will have a PROM and be very careful with the PROM if you do have one to remove and install because it can easily be damaged, and if it is a necessary procedure to change the PROM, then the ECM/ECC that you purchased should come with a detailed diagram and procedure for you to follow so that the PROM is properly installed into the ECM/ECC.

Here are two links that show the price of the ECM/ECC from a major auto part store depending on if the vehicle has a 2.5 liter 4 cylinder engine, or a 3.3 liter V-6 engine.

Link for 2.5 liter engine.
http://www.kragen.com/ProductDetail.aspx?MfrCode=A1C&MfrPartNumber=777748&PartType=248&PTSet=A


Link for 3.3 liter engine.
http://www.kragen.com/ProductDetail.aspx?MfrCode=A1C&MfrPartNumber=778706&PartType=248&PTSet=A

If you do not refill the filter housing after replacing the fuel filter there is another way to refill the housing.
after the filter is replaced and the cap is secured turn the ignition to run for about 5 seconds then turn to off. again turn to run for about 5 seconds then turn off. Repeat this about 8 to 10 times and then start the engine.
What happens is that every time you turn the ignition to run the fuel pump attempts to pressurize the line then shuts off. That is why you have to repeat the process.
While the truck is running the power to run the fuel pump comes from ecm. Some kind of safety function Dodge has built into the system so fuel will not continue to run if the engine is shut off.

I have a 2000 dodge ram. I had the same problem the truck would just stall no matter how fast or slow i was going. It ended up being the crankshaft position sensor. You need to check for codes to find the problem. p0385-p0389 is the crank shaft sensor. It takes about 5 min. to change if thats the problem. On that year you might be able to turn the key to the on position but not starting then off, then on, then off, then on (three times) on the third time leave on and watch the odometer it will flash codes then will say p-done.

the auto shut down relay supplies the voltage for the coil and injectors. it is activated by the powertrain control module. the pcm will not activate it if it doesnt get a signal from the cam or crank sensor or if the vehicle dont start due to a lack of fuel it will shut the signal off.