You should get power to the coil at key on for about three seconds, and then it should come back on while cranking the engine. Does it actually do that? If it does, disconnect the cam position sensor, (in the distributor) and try again, still see the proper behavior.?

 

When the key is put in the Run position power to the ignition coil does come on for 3 seconds and then goes out. It comes back on when you crank the engine. The problem is the ground pulse to the coil doesn't seem to be working. Please explain what disconnecting the camshaft sensor in the distributor will do? Will it stop the12volt from coming on in the Run position or while cranking? Or is this a test just to see if the camshaft sensor is bad? If it is bad would that prevent the computer from generating ignition pulses? In which case a new camshaft sensor is indicated? I would like to understand the diagnosis. Thanks. Louis

 

According to theory....... the pcm will trip the ASD relay again if it sees the engine turning via the cam, or crank sensor. Now, most of the time, (in my experience) if the crank sensor is bad, you will see power at initial key on, but, that's it. Disconnecting the cam sensor, and retesting is to see if you still get power while cranking. Which would imply the crank sensor is good. If you don't, that would imply the crank sensor is bad, and the cam sensor is good.

It's pretty much a shot in the dark, as what they suggest in theory, doesn't always apply to what actually happens.

So, if you still get power at the coil while cranking without the cam sensor, I would suspect the PCM has failed....... but, that *should* set a code. Should........

 

You said if you still get power at the coil while cranking without the cam sensor, you would suspect the PCM has failed? Wouldn't you suspect the cam sensor has failed? I would suspect a problem with the PCM only if I first disconnect the cam sensor and then disconnect the crank sensor and still get power at the coil for each case. Please clarify when you would think the cam sensor is bad? Thanks. Louis

 

You *should* see power for a few seconds at Key On, regardless of any failed sensors. It's entirely possible the PCM is seeing the cam sensor change state, and interpreting that as the engine turning, so, it sends power to the injectors/coil via the ASD relay, but, if it isn't getting signal from the crank sensor, it will never fire the coil. If the PCM sends power to the coil with the cam sensor disconnected, that implies the crank sensor is actually doing its job, and the problem is elsewhere. As you know the wire is good, and you tried another coil, that leaves the PCM.

 

I guess I'm still a little bit confused . You said earlier if the the PCM sees a signal from either the cam or crank sensor it will assume the engine is turning and send power to the ignition coil. So if the crank sensor is good but the cam sensor is bad will the PCM still try to fire the ignition coil? I still don't understand what happens when the camshaft sensor goes bad. I understand that if the crankshaft sensor is bad the voltage to the ignition coil will not exist during cranking. Since it did exist when the camshaft was connected it implies the camshaft is good and the crank is bad. But if the camshaft is bad and the crankshaft is good what happens???

 

Without the cam sensor, the ECU has no idea when to fire the injectors to sync properly.

It may also not fire the coil, but since I didn't write the code, nor have I talked to anyone who knows the code, I can't say yay or nay on that.

I suggest trying what HeyYou suggested, and avoid a "paralysis by analysis". We can always figure out why it worked later.

RwP

 

I attempted what HeyYou suggested but i couldnt find the connector for the camshaft sensor. I ran my hand around the base of the distributor from the driver's side of the truck and found a three wire set that went down the back and under the firewall. After probing further down, I found two connector sets at that location but was not able to pull them up into view
i assume one is for the cam and the other is for the crank but how the heck do you pull those connectors apart at that location with just one hand??? Are there any videos you can suggest that might guide me? Thanks. Louis

 

They do make them fun to get to...... Maybe have a look from underneath? Or see if you can unclip the harness from whatever is holding it in place, and pull it up where you can actually see it.... I'm used to working on full-sized trucks, so, while it is still tight, there is almost enough room.

 

My attempts to disconnect the camshaft sensor connector with one hand were not successful. However, before going through the gymnastics needed to get that connector appart another perhaps easier option came to mind. If i were to disconnect the PCM connector and power the camshaft sensor with a 9V battery and use a digital volt meter to monitor the camshaft sensor's output signal while cranking the engine. And if the meter read alternately between 0 and 8 volts while cranking then this would indicate the sensor was good.A similar test can be done for the crankshaft sensor. All i would need to know are the correct connector pins on the PCM connector to pull this off. I was hoping you can confirm which pins those are from your FSM. Can i have your thoughts on this approach? Thanks. Louis