Originally Posted by USAF90
im havin problems figureing out why im not getting power to my coil. ive looked at some wire diagrams and that stuff is like russian to me. only know basic wiring knowledge.
anyway, the motor is turning over fine, and tested most everything to start the engine. the fault lead me to the coil pigtail. and as you all know the pigtail leads straight into the wiring harness and splits off in every direction. does anyone know where the coil wires lead directly to so i dnt have to tear open every wire wrap?? any troubleshooting tech? any help at all would be great.. im facin up against my worst enemy right now.
also another thing, i cut the insolater directly on the wire to show some of the copper/brass metal, and put my voltameter on the wire itself instead of the plug. the ohms jumped up "BARELY" .. so something is restricting it. let me know if you need more info or anything else i should test.. thnx guys
Here's some help that I just threw together for you:
TO answer your questions and provide some general information on the wiring for the coil:
This is a lot simpler than you think. At the coil input, there's a hot wire (+) CKT A141 16AWG DG/OR. This wire can be traced directly to the power terminal at the PDC at the ASD relay PIN 30. This is your hot (+) feed that gets routed / switched at the ASD relay by the PCM when you start the engine. This is the wire that supplies the coil input with + voltage. Your going to want to verify voltage is present there and that it's ~ 12-volts. Once you've done that, now, your going to take a measurement at the coil INPUT to ensure voltage is also seen at the coil.
This can be done by having someone turn the key to <ON>. You must backprobe the connector with a paperclip attached to the POS probe into the POS (+) DG/OR contact hole. Don't cut the wire insulation for that's going to create issues later on. Never cut or puncture the insulation and, if you do, it must be sealed back up with silicone. Now, once you've backprobed the connector, connect the ground (COM) of the meter to a frame ground. Turn the key to <ON> and note voltage. It should be around battery range ~12-13 volts. You've got three seconds to snap a reading before the PCM kills the ASD relay due to no engine running condition is detected at the PCM level. It's a failsafe mechanism programmed into the PCM.
The PCM grounds the coil side of the relay through terminal number 85.
Terminal number 86 supplies voltage to the coil side of the relay.
When the PCM de-energizes the ASD and fuel pump relays, terminal number 87A connects to terminal 30. This is the <OFF> position. In the off position, voltage is not supplied to the rest of the CKT Terminal 87A is the center terminal on the relay
When the PCM energizes the ASD and fuel pump relays, terminal 87 connects to terminal 30. This is the <ON> position. Terminal 87 supplies voltage to the rest of the CKT.
SO, once you know how the CKT functions, you can easily go in and test at the various points to measure the voltages at each point along with measuring the resistance of the hot wire. The resistance should ~ 0 OHMS for both the POS and NEG wires. NOTE: disconnect the NEG bat lead when performing a cont / OHM test. Reason: it is possible to slip with the meter probe and dead short to ground which is pretty violent at that amperage and may do some damage depending on where it shorts to.
Now, there's another section of this CKT and that is the ground at the coil. The black wire goes from that pigtail to the harness all the way to one of the multi pin connectors at the PCM. I believe it's the black connector where all grounds are tied into. I do not recall which PIN it connects to so, you'll have to trace it out with a meter or, I can look at the schematics when I get home and post exactly which pin it is so that you don't have to guess or trace it out.
Just because you may not see input voltage at the coil input does NOT mean that there's an issue with the supply. It may very well be due to a combination of several different things however, you must at least test the ASD relay in both powered and NON-powered modes to ensure that it is functioning correctly as well as verifying power at PIN 30. IF there's power here, and the ASD is working, then, we can move to looking at the coil input to testing of the coil itself on the primary and secondary. This too is very simple to do yourself.
Here's HOW to test the coil:
Diamond Primary 0.97 - 1.18 Ohm
Toyodenso Primary 0.95 - 1.20 Ohms
Diamond: 11,300 - 15,300 Ohms
Toyo 11,300 - 13,300 Ohms
Take the meter and measure the OHMs by measuring between the ground and hot (primary) at the coil input along with the hot to coil output (secondary)
HERE's HOW to test the ASD relay.
- With the relay removed from the vehicle, use an ohmmeter to check the resistance between terminals 85 and 86. The resistance should be 75 ohms +/- 5 ohms.
- Connect the ohmmeter between terminals 30 and 87A. The ohmmeter should show continuity between terminals 30 and 87A.
- Connect the ohmmeter between terminals 87 and 30. The ohmmeter should not show continuity at this time.
- Connect one end of a jumper wire (16 gauge or smaller) to relay terminal 85. Connect the other end of the jumper wire to the ground side of a 12 volt power source.
- Connect one end of another jumper wire (16 gauge or smaller) to the power side of the 12 volt power source. Do not attach the other end of the jumper wire to the relay at this time.
CAUTION: DO NOT ALLOW OHMMETER TO CONTACT
TERMINALS 85 OR 86 DURING THIS TEST.
DAMAGE TO OHMMETER MAY RESULT.
- Attach the other end of the jumper wire to relay terminal 86. This activates the relay. The ohmmeter should now show continuity between relay terminals 87 and 30. The ohmmeter should not show continuity between relay terminals 87A and 30.
- Disconnect jumper wires.
- Replace the relay if it did not pass the continuity and resistance tests. If the relay passed the tests, it operates properly.
Below is the ground side faults:
- the ground that goes from the coil TO the PCM is at high resistance thus dropping voltage at the coil input.
- the ground that goes from the coil to the PCM is OPEN due to damaged wire / contact pin at connector at PCM.
- the ground is not being switched ON/OFF at the PCM NOTE: this is very common by the way. I had it happen on my Dodge and, in my case, it was intermittent.
In the case of a blown coil driver CKT- you must buy a new PCM.
TO TEST THE COIL DRIVER CKT:
LED test light.
Connect one end of the test light to the negative side of the coil- BLK and one end to the headlight ground at the frame rail.
IF IT's working: the light will pulse. IF NOT; there won't be any light at all or, it will be on 100% meaning, the coil driver CKT is stuck <ON>
Either way, this indicates that the PCM is malfunction and it must be R&R. (remove replace)
EDIT: Additional information on the coil driver CKT / diagram:
Your going to see three multipin connectors at the PCM. From left to right they are GRAY, WHITE and BLACK if memory serves me correct.
Now, the black one contains the ground for the coil No 1 driver. The CKT is K19 16BK/GY. This meaning, the wire your looking for is a 16AWG wire that is black and grey. The respective pin designated on the drawings I have state A7. However, having worked on this system many times, based on my memory, this does not correlate to the PIN-out at the connector so, what you need to do is this:
1. Disconnect NEG bat cable.
2. This step has two options for draining power out of the input section of the PCM
OPTION A: Either wait for apx 15 minutes or so for all power to drain out or
OPTION B: Using a 1M 5W resistor, tie one end to the NEG bat cable and touch the other side of the resistor to the POS (+)(method I use because I don't like to wait)
This will gently drain all power in seconds vs minutes and will not arc, spark, or otherwise kill / damage the caps. In general, if you've not used this method before, simply allow ample time for all power to drain out.
NOTE: By turning the key to <ON> or stomping on the brake, turning on the headlamps, pressing the horn etc etc, will not work to drain power from the PCM due to the fact that there's no ground CKT to complete the path to ground.
Ok, so now that all PWR has been drained out of the PCM:
-Remove the BLACK connector and place it where you can get access to the pin contacts inside.
-USING ONLY A PAPER CLIP, attach the paper clip to one of the DMM probes.
-Tie the COM lead to the coil GROUND pin by backprobing it with another paperclip attached to the NEG DMM probe.
-SET METER TO CONTINUITY / BEEP
-Probe the black multipin connector until you find the respective contact pin
-NOTE OHM reading- should read near zero OHMs.
Once that is verified, that's as far as you can verify at this point. The rest of the CKT resides inside the PCM. This is what is called the Coil No 1 DRIVER. This is what is responsible for switching the coil ON/OFF.