Hello and welcome to Just Answer!
It sounds like there is something taking the PCM down! Can you disconnect the 8 way round solenoid connector from the transmission and see if the engine will start?
Let me know!
Let me know when you are ready to do some testing and I will help you solve this!
Does the starter crank the engine over good like before or does it seem like it drags and the engine turns over slow?
Can you take a voltage reading of the battery and then try and start your truck and see what the voltage drops to? I would like to know what the battery voltage is before and during cranking!
The PCM won't communicate with the scanner because either the 5 volt sensor supply is going down or the PCM is faulty. The PCM sends out a 5 volt reference to sensors like the crank sensor, cam sensor and etc and when this voltage gets shorted to ground, the PCM will get taken down and the fuel & volt gauges won't work and the PCM won't communicate with a scan tool.
When would you have time to run through some tests with me? I am a full time tech during the day, but will be online this evening and tomorrow.
If you have no draw on the battery, then the battery must be faulty and won't hold charge.
The best way to check for draw is by using a amp meter in series with the battery cable and post, it doesn't matter which cable.
Let me know and we can go from there!
I asked you to check the voltage at the throttle position sensor violet/white wire, not the speed sensor voltage!
Did you check that wire for voltage with the key on?
If the starter cranks the engine over good, then the battery is likely ok for testing.
Lets see where the draw is coming from. Hook up your amp meter and watch it as you pull all the fuses out one at a time. Once you pull one out and the draw doesn't change install that one and move to the next until you find the one that drops the current draw. Start with the interior fuse box first! You will have to wedge something in between the door and the door ajar switch near the door hinge so the button stays pressed in while you check this.
Remember not to open the doors or turn any accessories on while your meter is hooked up, you could burn the fuse in your meter if you do.
0.005 amps is only 5 milliamps and won't kill a good battery in a couple months. It would take a long time to kill a battery at only 5 milliamps. I thought you said it was .9 amps draw, what were you using to check that?
The PCM is down so we need to check the PCM for power and grounds.
Do you happen to have a 12 volt sealed beam headlight or bulb kicking around? We need to load test all the power and grounds to the PCM.
We need to remove the C1 connector from the PCM which is the connector closest to the engine. The PCM is on the pass side firewall! Hook the bulb up according to my picture for checking power then to check for ground move the wire from the negative post to the positive post.
Check terminal #2 light green/black wire for key on power.
Check terminal #22 red/white wire for battery power.
Check terminal #31 & 32 black/tan wires for ground.
Let me know what you find!
Can you measure the battery voltage while cranking the engine over and let me know what it reads?
Checking the voltage at the TPS won't really tell us the PCM is bad, it will tell us if the 5 volt reference voltage is down.
If you checked the 5 volt supply wire(violet/white) at the crank sensor for voltage and you got no voltage with the key on, then the 5 volt supply is down or the PCM is down!
I need you to turn the key on and check the battery voltage at the battery, if the battery voltage is around 12 volts, I would like you to double check the violet/white wire for power. If you don't have 5 volts, we need to start disconnecting all the sensors one at a time to see if one of the sensors is taking down the voltage.
Let me know when you are ready to do this and I will walk you through the tests!
I would like you to disconnect the transmission 8 way round solenoid connector and test the voltage at the crank sensor violet/white wire, you should have 5 volts and if you still don't get 5 volts, visually check the harness from the solenoid connector up to the engine to make sure the wiring isn't pinched, cut, or has a bare spot and is touching ground. If it all looks ok, I will need you to disconnect the camshaft position sensor and re-test the voltage to the violet/white wire at the cam sensor connector. The camshaft position sensor is located on the timing chain case/cover on the left-front side of the engine. You should have 5 volts and if you don't disconnect the throttle position sensor, then the map sensor and let me know the results.
Yes, the PCM has failed! Since you checked the harness that runs down to the transmission for short to ground on the orange wire and no short found, the PCM must have failed. To make sure the harness is ok, you could cut the orange and violet/white wire a few inches away from the PCM and then turn the key on and measure the voltage on those wires on the PCM side. This would rule out a short to ground on those wires. After testing those wires re-connect them using a non insulated butt connector, crimp, solder and heat shrink the connection.
The oem part # XXXXX 56046359AA and it changes up 6 times from the original #. Here are all the numbers that will work n your truck! 56046359AA, 56046359AB, 56046359AC, 56046359AD, 56046359AE, 56046359AF and R6046359AF. If you want to check on a used PCM, it can have any of those numbers.
Here are some sites that might have the part, The first one is a used parts locator and the nest two are new parts locator.
I hope this helps!
You're welcome, let me know how you make out!
Yes you can, but you will need to check for continuity to ground on those to wires. You will need to disconnect all three PCM connectors and then set your meter to read ohms and put one lead of your meter to the orange wire and the other lead to ground. You shouldn't get any reading on your meter(open). Repeat test for the other wire.
The violet/white wire is in pin # 17 of the c1 connector(closest to the engine)
The orange wire is in pin # 31 in the c2 connector(middle).
When all sensors were disconnected there were no reading on the C-1,C-2 pins.
However, when all the connectors were connected back we got a reading on the C2-31 of 2M ohms.
It is normal to see a reading like that with all the sensors connected. That is a very high resistance, so there is nothing to be concerned about that. You will need a PCM, we have throughly checked everything possible!
Let me know how you make out!
Last Friday I installed the computer in the truck and it fired up. Thanks,
That's great, I'm happy to hear that!!