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I have a 2003 Ran 1500 with a gas guzzling 4.7L. When starting the vehicle I inadvertently took my hand off of the key at the very instant that the engine was igniting. The engine did not start and now will not start. The yellow “check engine†light came on. The codes were P0685 (Auto Shutdown Relay Control Circuit) and P0688 (Auto Shutdown Relay Sensor Circuit Low). I checked all of the relays and ran a continuity test on the control circuit line, but could not find anything wrong. After resetting the codes with my Maxi-Scan (MS509) code reader I was unsuccessful when trying to start the engine, but this time, the yellow “check engine†light indicated code P0129 (barometric pressure low). I tested the MAP sensor, but it too checked out to be good. After resetting the yellow “check engine†light again the vehicle still will not start. The yellow “check engine†light came back on but it is not indicating any code. I’ve been told by another backyard auto enthusiast that I may need to have the computer reprogrammed. I want to get your expert advice before I have to remortgage the farm to pay the Dealer’s exorbitant hourly rates.
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No codes, I would start first by checking fuel pressure, spark, and air. See if one is missing. Hope it is not the computer.
Man, this is a good one. I’m curious to see how it shakes out. Just so you know, you can go to alldata.com, which is my favorite all-encompassing service information site, and click on the alldata-diy button, and for 25 bucks, you can buy a one year membership for your particular vehicle. I’m not trying to sell anything, but in school, that was my favorite site vs. Mitchell and even the manufacturer specific sites, excluding technical service bulletins. Waaaaaaay better than Haynes manuals in my opinion.
Not sure if its a common problem with Dodge vehicles, but GM’s SUVs (trailblazer, envoy, etc) had a common problem with the ignition switch. When they went bad, random warning lights would come on, gauges were going haywire, no start issues, or sometimes the vehicle would die. Have you tried disconnecting your battery to reset everything?
Just saying: Usually when the MIL is on and you can’t retrieve any codes, make sure you have power going to the OBD port. Its common for the fuse to blow sometimes as its usually run on the same circuit as the cigarette lighter.
I will agree with wardak33 and try disconnectiong your battery for a while to reset everything. If it just happened that one time after you let go of the key when it was about to start then maybe the computer needs to be reset. Now I did have to replace the ignition swith in my 04 Ram so I wouldnt put it past that. The ignition switch was pretty easy to do and it didnt cost much (it will cost more if you want to have the same key as door and ignition but i didnt care) I have 175,000+ miles on my Hemi Ram and have had to replace a ton o parts on it
I think in your situation you need to figure out if if’s a computer control issue or a mechanical issue. I’m not familiar with Dodge systems but I’m thinking the ASD relay is what turns on the fuel pump and I think the computer when you start the car, if the computer doesn’t get power it won’t be able to turn on the injectors and everything else that it does to get the enigne going. You might first start by checking for spark and fuel, if you have one or the other then I would look to the one that is missing, i.e. if you don’t have fuel but have spark check the fuel circuit but if your missing both then I would look to that relay circuit to see if it’s working properly because if it’s not powering up vital circuits it won’t start. Good luck.
Quoted From EricTheCarGuy:
I think in your situation you need to figure out if if’s a computer control issue or a mechanical issue. I’m not familiar with Dodge systems but I’m thinking the ASD relay is what turns on the fuel pump and I think the computer when you start the car, if the computer doesn’t get power it won’t be able to turn on the injectors and everything else that it does to get the enigne going. You might first start by checking for spark and fuel, if you have one or the other then I would look to the one that is missing, i.e. if you don’t have fuel but have spark check the fuel circuit but if your missing both then I would look to that relay circuit to see if it’s working properly because if it’s not powering up vital circuits it won’t start. Good luck.
Well seems like I am not the only one with this problem, I have a 1993 Dodge Ram 350 I see spark but not fuel, so checked t relays in off position n everything looks ok, check in ingnition on n the wire that goes to t pcm indicates about 7 to 8 volts, I guess it should indicate 0 cause the pcm supplies t ground, if somebody can help me, on this one thanks
If its an ASD issue, your going to need to fnd some wiring diagrams and start from there, again +1 to Erics post.
Thank you again to Jacobnbr1 for posting the diagnostic algorithm.
I find it interesting to see these two different diagnostic approaches to the problem. On the one side is the basic conceptual model of fuel, spark, and mechanical problem solving. On the other side is the approach devised by OEM engineers who designed the system, first this, then that, etc.
No doubt, both approaches have their role, and both will take you to the solution, eventually. Having the experience to know when one approach will get you faster is the sign of experience.
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