Working on trying to get a 95 ram 5.2 running. I noticed a code for the ASD relay, code 42 by doing the on-off-on-off-on thing with the key. I checked the asd relay and found it's not switching on when the key is put to the run position.

I have found a problem to be the wire the ECU uses to ground the relay to make it switch on. A wire my diagram calls ASD relay control. I checked it with my multimeter and with one end on this wire and the other end to battery +, I get 12v whether the key is on or not. Looking at a wiring diagram, it looks to me like the computer is supposed to ground this pin when I turn the key to run, yet this is not turning the relay on. I have spare relays and tried them to no help. I disconnected this wire and ran a wire straight from the relay to ground, causing the relay to turn on and the fuel pump to turn on. When I hit the key it starts and runs for about a second then dies. Any ideas? Sound like my ECU is bad? I followed the wire back to the computer and checked for resistance and it's all good.

Your correct in that the PCM does ground that pin to energize the relay. Note though, the PCM must see the engine pulses (crank sensor) turning to keep the ASD relay energized, if not it times out after a few seconds. So you would have to check this wire right when you key on to crank to see if the pcm is actually grounding it. That would show the PCM is grounding it so that part of the circutry is working. You grounded the wire yourself to get the fuel pump on and ASD relay energized, but if the crank sensor is not putting out a signal you would get a start-flare based off the fuel squirted in for the engine prime fuel shot, but would die right after if the PCM does not see the crank pulses to keep the injectors firing in sequence. So I would check to make sure the crank position sensor is working. You can do that by connecting a meter with a needle on it across the crank sensor and cranking the engine and seeing if you see the voltage 0-5 volts change while cranking.

If you do need a PCM, I have a new ones (56026790)or(56028322)in the box

before you go the computer route,make sure you don't have a broken/corroded wire.there is a splice in the taped harness that branchs off into many different circuits. corrosion gets there-creates bad connection.I think the asd relay should have 2 positive wires 1 battery + and 1 with the key on.Use the wire schematic,Check the computer harness make sure you have all power and grounds going to it. The ground on the engine also goes bad.battery cable,also main harness ground all on the same stud. if all ok, yes the computer controls ground. for test purposing you can ground/jump the relay,see if that is the only problem. use a fused jumper wire.

Thanks for the input. I went through everything, cleaned the connectors and put everything back the way it was supposed to be. The ASD code is gone but I'm getting code 11. Looked it up and that one sounds like a code for a crankshaft position sensor.

I checked the crank sensor wires. With the sensor unplugged, I get 5v, 7.4v and ground. With the sensor plugged in the 5v drops to 2.4v and it does not seem to pulse when the engine is cranked over. I only have a digital multimeter but it does have a min/max function and it wasn't showing any changes while cranking. Time to try a different crank sensor I guess.

The crank sensor has three wires as you know. The signal wire which is 5 volts from the PCM looking to ground and go to 0 volts. One wire is a ground and the other is the power up circuit for the sensor. Some use 12 volts and some use 8 to 9 volts and some even use 5 volts to power them. I believe yours is an 8 volt power up circuit. At 7.4 you may just have a slightly low battery. But the 5 volt signal wire should be either 5 or 0 volts. Unhook the sensor and make sure it reads 5 volts and then ground the wire and make sure it reads 0. If it does it sounds like the crank sensor is the problem but you might want to check the wire diagrahm to make sure the power up circuit is an 8 volt circuit to make sure its not a 12 volt power up circuit which would of course mean a wire problem or PCM problem. I have been away from turning wrenches for 2 years but I think everytime you ground the 5 volt signal circuit with the key on the auto shutdown relay should energize. If you dont have acess to a wire diagrahm let me know as I can still get on the Mopar site and get the wireing for you . Ron

Hi Ron, thanks for the info. The engine harness diagram I have and the ECU pinout diagram I have are for a 94 so some of the colors are different but the connector pinouts seem to be the same so I've been able to follow them. My diagram shows it should be a 8v feed for that sensor and it's only reading 7.4v. I had the battery charger on it for a while and topped up the battery before checking. Not sure if 7.4 is unusual. I'll check out grounding the 5v wiring in the morning, but it was showing 5v when the crank sensor was unplugged, dropping down to around 2.5v when the sensor was plugged back in. Thanks, Tristan.

As said the crank position sensor is a hall effect sensor. The feed is 8volts from the PCM, If your reading 7.4v thats okay as it also is feeding the cam sensor and there will be a voltage drop when reading this. The signal coming from the crank sensor to the PCM is a square wave 0-5 volts. 5 volts when there is no metal in front of the sensor head and 0 volts when the tooth passes in front of the head. So if you back pin the sensor (put meter between ground and signal out)and crank the engine you should see the pulses (0-5 volts). It does take a while to set the code 11. A lot of cranking with no signal. You might have set this code if you tried cranking the engine with the sensor disconnected. Either way, back pin the sensor, crank the engine and see if you get the pulses (0-5volts)

Its actually the transition from low to high if memory serves me correct (or vice versa). There is a pattern used, there is more than one tooth/space whatever that application used. The holes or teeth depending on manual/auto application. I believe that system used 4 even markings for one cylinder and a larger gap and three markings so the PCM can detrmine which cylinder is coming up based on the larger gap and the cam sensor input.

Pulled out the crank sensor and it's quite mangled. It appears that the bottom or "face" of the crank sensor was rubbing up against the tone ring on the flywheel. The crank sensor is grooved quite bad in this area. I grabbed a spare from the junkyard, what a HUGE pain in the ass that was to pull. I mocked it up by hand and it feels like this crank sensor is also touching the tone ring if I was to bolt it down. It looks like I will have to shim up the sensor so it doesn't physically touch the tone ring. I don't get how or why this is a problem. The engine is just a regular 5.2 magnum and the flywheel is one that 70cuda383 hooked me up with (thanks again for that!) which I'm pretty sure he said was behind a magnum 5.2. The engine itself is a 99 however all the electronics are 1995.

Well my bad. I have now come to learn that auto trans and manual trans did not use the same crank sensor.

I do remember a TSB on shimming the crank sensor to stop it from hitting the flywheel. But I dont remember if it applies to your truck. You have to fix it no matter if it hits with the right sensor in there. Just shim it some and it should work fine. If you were reading 2.4 volts on the 5 volt signal wire then that does sound like a bad crank sensor as was said it should be 5 or 0 volts. Sounds like the crank sensor was shorting to ground some internally. Good luck with it , Ron

Finally got around to throwing in the correct sensor today. Fits nicely. Hit the key and same thing as before, vroom runs for 2 seconds then quits. Computer is still spitting out code 11 - no crankshaft signal. I have a hard time believing this because if I try and crank it with the sensor disconnected it doesn't try to fire. Same thing if I crank it with the sensor plugged in but unbolted from its hole. So obviously the computer is getting a crankshaft sensor signal. Checked the ground for the crank sensor, it's good, less than 1 ohm of resistance. Checked the wire that's labeled in my diagram as the crankshaft position sensor signal and it's a solid 5.02 volts. The 3rd wire, the one labeled as 8v supply is still only putting out 7.3v at the crank sensor plug, distributor plug and even right at the ECU. Tried it with the battery charger hooked up to make sure I wasn't running low on power and no change. Not sure if this is an issue? ECU is out of the junkyard so I can only assume it was a running vehicle. Any other ideas? I was thinking to pick up a spare ECU at the junkyard to see if that's my problem?? I'm at a loss and annoyed at fighting with this same issue. Power wires, ground wires, everything is new because I went thru it all during the engine swap.