Mechanics

ENGINE TURNS OVER BUT WONT START

2001 Dodge Intrepid • 200,000 miles

I got in my wife's intrepid to go to the store and it just cranks and cranks. There is no power to the inj/coil fuse, or the 02ssr fuse in the power distribution box under the hood. I had the odb2 run on it the two codes that came up were p0700, and p1698. I'm not sure where to go from here, I dont know where to start tracking down wiring or anything. Do I need to look at replacing the tcm and pcm. The car is over 11 years old and has a lot of miles on it, I'm not sure if it is worth the money or not. Any advice is going to be verry helpfull.
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Craig jaster
November 22, 2011.




The tcm and pcm are the very last things you look at. First of all, you need to get power to the fuse box for the accessories. I would check all the fusible links by the battery for one that is open. If there is, you need to find out why it burned up as it does not blow without a good reason. It may be wiring, or a failed component.

If you are not sure, let a shop do this for you that is expierenced at these types of repairs. It will cost you but is better than throwing parts at it that do not repair anything.

Roy

ASEMaster6371
Nov 22, 2011.
I swapped the relays around and nothing changed I will go through the fusible links to see what I can find open and go from there
Thanks

Tiny
Craig jaster
Nov 22, 2011.
Any chance you might be able to tell me where to find any more than the one between the battery and the altenator

Tiny
Craig jaster
Nov 22, 2011.
The fuse panel does have power, its just those 2 fuses that dont have any voltage thats why I am having so much trouble figuring it out.
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Tiny
Craig jaster
Nov 22, 2011.
There should be a group of them. Look around the fuse box. There may be 6 or 7 of them together.

Roy

ASEMaster6371
Nov 22, 2011.
You have to check for voltage while cranking the engine. Voltage will appear at the coil, injectors, alternator field, and oxygen sensor heaters for only one second after turning the ignition switch to "run", then the voltage will go to 0 volts. You might hear the hum of the fuel pump for that one second. The voltage will come back during engine rotation, (cranking or running). It comes through the automatic shutdown (ASD) relay. The Engine Computer, (PCM), turns the ASD relay on when it receives pulses from the camshaft position sensor and the crankshaft position sensor. Somewhere around the early to mid 2000s they changed the strategy so the engine could still run when one of those sensors failed but before that signals were needed from both sensors for the ASD relay to turn on.

To test the entire ASD switched circuit, connect a test light to the positive ignition coil wire, the 12 volt feed wire to any injector, or either small wire on the back of the alternator. The 12 volt feed wire is often dark green / orange. Whatever the color, it will be the same on all injectors and the coil. Watch for the test light to light up for one second when you turn on the ignition switch. A digital voltmeter might not respond fast enough for you to see it. If you see that one-second pulse, the ASD relay and wiring are okay and the computer has control of it. No need to check fuses.

What's important is if that voltage comes back during cranking. In the rare event it does, you have to determine if you're missing spark or fuel pressure. Usually it will be the fuel pump that fails to start up. Banging on the bottom of the tank often gets them going. Unlike GM fuel pumps that suddenly leave you sitting on the side of the highway, Chrysler pumps almost never quit while they're running. They typically intermittently fail to start up after being turned off.

There have been times no diagnostic fault code is set related to the cam and crank sensors. In that case it is helpful to have the Chrysler DRB3 scanner connected or an aftermarket scanner that can display live sensor data and has a "no-start" troubleshooting menu. It will display those two sensors with "no" or "present" to indicate if signals are being received from the sensors. Even if it does finally set a code related to a sensor, that never means "replace the sensor". While it's true the sensor is usually the cause of the problem, the code really means that's the circuit that needs further diagnosis. There could be a wiring problem such as a corroded connector pin or cut wire.

One of the strategies the Engine Computer uses to know when to set a fault code is if it's getting a signal from one sensor, it had better be getting a signal from the other one. They have their ground return wire and 5 volt, 8 volt, or 10 volt feed wire in common. If either of those wires are open circuit, (cut, or corroded at the splice), neither sensor will produce a signal. The computer will not know the engine is rotating so it won't set a fault code related to the two missing signals.

Caradiodoc
Nov 22, 2011.
No luck on any other fusible links. The codes are saying that there is no bus communication between the pcm and tcm and the tcm has a fault code also. So if there is a broke wire in between the two I guess that might explain the codes. I do have voltage to the asd relay which is what supplies power to those two fuses. Acording to the haynes manual, the pci supplies ground to them, and the both have ground. Do I need to be looking for a break between the asd relay and the 02ssr fuse then? This is a huge mess here.

Tiny
Craig jaster
Nov 22, 2011.
That should be helpful, I know the fuel pump is going, I can start the engine if I jump a positive to the inj/coil fuse in the power distribution box, then the car runs and drives fine, but the alternator doesnt charge the battery, and the indicator lights and gauges on the dash go crazy.

Tiny
Craig jaster
Nov 22, 2011.
I think you've unknowingly identified the problem. Measure the voltages on all three wires on the back of the alternator while the engine is running. You'll find full battery voltage on the large output wire bolted to the back. One small wire must also have full battery voltage. The other one will have less but not 0 volts. 4 - 11 volts is typical. I suspect you're going to find 0 volts on both small wires. Since you're jumping battery voltage to the coil / injectors and the engine runs, the alternator is on that same circuit, ... It should be working too. If you find 0 volts on the small wires, there has to be a break at the splice for all the wires in that circuit.

If you do find battery voltage on one small alternator wire, and the same voltage on the other one, that would suggest the Engine Computer isn't turning on the voltage regulator built into it, and that's why the alternator isn't recharging the battery. That would point to some other cause.

Of course there could be two totally separate problems but that isn't real common. It IS common for the brushes to wear in the alternator and cause intermittent charging. Those brushes can be replaced easily, often without even removing the alternator from the engine. That problem should be addressed last though because it won't be related to the no-start problem.

Caradiodoc
Nov 22, 2011.
Ok so I took the alternater off and had it tested and it was bad, so I buy a new one ($100 that I dont have) and now it still wont start any other ideas out there?

Tiny
Craig jaster
Nov 24, 2011.

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