| I originally made this thread on 300zxclub but figured I would post it here to try to help people as well. (for the life of me I cant get the IMG tags and Links to work properly on this site, if I get an image working, the next paragraph or so disappears for some reason, If someone knew how to fix that, that would be great... original thread - [ http://www.300zxclub.com/showthread.php?p=1965559#post1965559 ])
How to trouble shoot a code 21/no spark issue. This is mainly for no spark on ANY cylinder issue. But also can be used for no spark on individual cylinders.
I highly recommend getting a free pdf version of the FSM (factor service manual) an online one can be found in the FAQ's
section, but it suggest downloading the 1994 version from here [ http://simsters.com/z32.htm ] and saving to your computer. TOP = Components and operation intro,
Lower = Short version
Lower yet = long version
Bottom = Just one cylinder not firing.
__________________________________________________________________________________________________ [ http://i48.tinypic.com/28guqs7.jpg ] The basic components for the ignition system are:
1. CAS (or crank angle sensor)
2. ECU (engine control unit or computer)
3. PTU (power transistor unit)
4. 6 ignition coils. (or coil packs)
5. Ignition Relay (relays constant power to the coil packs) The basic method of operation: The z32 does not have a distributor, instead it has individual coil packs mounted on top of each of the spark plugs to provide a high energy spark, for more efficient burning of fuel mixture and more power.
1. CAS: The spark is triggered by the CAS which is located on the front of the driver side exhaust camshaft. The CAS has a spindle that rotates with the camshaft and sends a signal to the ECU and tells it when to initiate spark. The CAS is shown in yellow here. [ http://i50.tinypic.com/11kwjfc.jpg ] 2. ECU: The ECU or engine computer is located behind the passenger side floor board. The ECU receives a signal from the CAS and sends signals via 6 wires to the PTU to initiate spark. 3. PTU: The PTU or (Power Transistor Unit) is either the old style (gray metal with fins) or new style (black plastic) and is originally mounted on the front of the passenger side timing cover. Because of heat issues causing the old metal gray ptu's to fail, they have been recalled and many have been relocated under the nose panel or somewhere similar. As shown in yellow here. [ http://i49.tinypic.com/in8vuq.jpg ] The PTU increases the voltage from the ECU from .5 volts to around 10,000 IIRC. The PTU has one ground wire going to it to complete the circuit. If this ground wire is not properly, you will permanently damage your PTU. One the new style (black plastic) PTU's the ground wire is the black one in the middle on the side that has 7 wires/terminals coming from it. On the old style PTU's it was on one side or the other IIRC. 4. COILS: After the current flows through the PTU it travels to the Ignition Coils, where it energizes the secondary circuit, when this circuit is de-engergized, the collapsing magnetic field creates intense voltage in the primary coil circuit up to 40,000 volts which brides the spark plug gap and creates a spark. 5. RELAY: The ignition relay is located in the fuse box in the engine bay on the driver side. When this coil is energized by turning the key to the on position, 12v constant power is provided to the middle terminal of the ignition coils.
Shown in yellow here. [ http://i45.tinypic.com/2n81lxx.jpg ] _________________________________________________________________________________________________ Trouble shooting: So your getting a code 21 and you have visually checked and you have no spark, now what? SHORT(er) VERSION 1. Turn the key to the on position, Grab your digital multi-meter and test for 12v at the middle terminal of the coil pack connectors (red arrow pictured below) with the negative probe on plenum ground. You should read battery voltage. [ http://i47.tinypic.com/es2knd.jpg ] this will check your constant power circuit and IGN relay.
_________________________________________________________________________________________________ 2. Next test for 12v at the middle terminal of the coil pack connectors with the negative on the smaller black wire of the coil pack connectors, (place the positive probe on the red arrow here and the negative on the green arrow) [ http://i47.tinypic.com/es2knd.jpg ] this will test your ground circuit.
_______________________________________________________________________________________________ If it passes both of these tests, then the issue is probably ptu related. To test the ptu follow this diagram found in the 94+ FSM.
[ http://i48.tinypic.com/6xt3s7.jpg ] If it passes the tests, try cleaning all the PTU connections, and make sure they are tight. If still no spark, check the ground circuit to the ptu. If you look below, the black wire in the middle of the connector with 7 wires coming from it is the ground circuit. Shown by the green arrow. [ http://i47.tinypic.com/dbtzkp.jpg ] Using your multi-meter, disconnect the connector and test that wire for continuity/ohms of resistance with plenum/body ground. It should be near zero. If you read a high resistance or infinite resistance, remove the PTU subharness and test again to remove a possible fault. If still a high/infinite resistance check the ground connects shown here, especially the one underneath shown in my picture. [ http://i46.tinypic.com/rbwmlz.jpg ]
[ http://i37.tinypic.com2a7x0ns.jpg ] the wire I'm holding is a ground wire that branches from the harness where the #4 and #6 coil pack connector wire branch off. If this isn't connected properly you WILL fry you ptu. It connects near the #6 cylinder behind the balance tube on the rear driverside of the engine.
__________________________________________________________________________________________________ If STILL high/infinite resistance, there may be a break in the wire, I suppose you could possibly wire up an external ground to the PTU just to see if it would fire then. I don't know if that would cause any problems, just an idea. I don't think it would because there should be zero ohms of resistance to ground anyways. __________________________________________________________________________________________________
If it passed all tests above for the constant 12v to coils circuit, and ground to coils circuit, ground to the PTU is good, and the PTU test good per the FSM.
Then the problem is most likely with the 6 signal wires to the PTU from the ECU and or the 6 wires from the PTU to the coils. (or a bad CAS or CAS connection, not sending the signal to the ECu to tell the coils to fire) Test each wire for continuity/ohms of resistance by touching one probe on the signal wire at the coil pack connectors (yellow arrow below) and the other probe to the corresponding terminal at the PTU connector, (E1 is for coil 1, E2 and coil 2 etc. I think) If those all check out then do the same thing with the wires from the ECu to the corresponding PTU terminals. Here is a pinout of the ECU. Make sure do disconnect the battery before disconnecting the ECU. [ http://i45.tinypic.com/54ww91.jpg ] If everything checks out, then just make sure all connectors are tight and clean. I could not figure out why my #1 coil wasn't firing. Everything check out. It turned out to be a loose connection at the ECU. Runs fine now.
Below is a more in-depth troubleshooting guide. _____________________________________________________________________________________________________
LONG VERSION Possible causes:
1. Bad PTU connection:
A: Well a lot of times, a no spark issue is caused by loose/dirty/corroded connections to the PTU since it gets exposed to the elements easily. Start by cleaning the connectors carefully, both the connectors directly on the PTU as well as the both of the subharness connectors a few inches away. B: A flathead screwdriver and a bit of sand paper seems to work pretty good for me, although there are other safer methods. C: When finished, coat the connections in di-electric grease to protect them from future corrosion, and see if that helps.
2. Bad PTU:
Ptu's occasionally go bad, especially if a ground isn't connected. Using a multi-meter or continuity tester you can test the PTU as outlined in the FSM here, [ http://i48.tinypic.com/6xt3s7.jpg ] A: note: polarity matters, make sure you have the positive/negative probes on the correct terminals, also because of the different styles of PTU's and different FSM testing diagrams, carefully study the testing diagram you are using. B: If you have a series 2 ptu I suggest downloading the 94+ FSM to find the correct diagram, If you have an old style PTU, use the pre-94 FSM.
3. Missing ground connections after plenum pull:
A: If you have recently pulled the plenum double and triple check ALL GROUND CONNECTIONS, especially this one that is mounted behind the balance tube on the driver side of the engine, very close to the #6 cylinder. [ http://i37.tinypic.com/2a7x0ns.jpg ] The ground wire branches from the main harness at the same place that the #4 and #6 coil pack wires branch from the main harness. If this ground is not tight and clean you WILL fry your PTU. (this is what happened to me after a plenum pull and I forgot to re-connect it. I could not figure it out for months, someone on tt.net suggested I check the grounds. Found the missing ground, connected it and it fired right up!)
4. Bad CAS connections:
A: If the connections to the CAS are dirty or corroded, or if the CAS just plain is dead, the ECU will not receive a signal to fire the spark plugs or injectors in the first place. B: Clean the connections to the CAS if they are dirty and try again. If still nothing, spin the CAS by hand with the key in the "ON" position, and you should hear the injectors click, as per my other write up here (not on this site) C: If you don't hear any of the injectors fire than either the connections to the CAS are dirty or the CAS itself may just be bad. (there may be some other causes that im not sure of, unless ALL of your injectors are dead which im not going to get into now)
5. Bad IGN relay:
A: The ignition relay provides the necessary constant power to the ignition coils. To test if the relay is working, simply turn the key to the "ON" position but NOT start. B: Then use a multi-meter or volt meter and test for around 12v (battery voltage) at the middle terminal of the coil pack connectors, harness side. With the negative probe on plenum ground. Pictured here by the red arrow. [ http://i47.tinypic.com/es2knd.jpg ] c: If the relay is working you will have around 12v (battery voltage) constant. D: If no voltage, then either the relay is bad, or there is no power to relay because of a open/broken wire going to and from the relay pictured here (red wires and yellow wire, and possibly orange wire from the ECU) [ http://i48.tinypic.com/eikbl.jpg ] E: You can either swap the relay with a known good one, or you can pull the relay and test for 12v on the top and bottom of the terminals that the relay plugs into, one the left side, and body/engine/plenum ground. test for 12v at the yellow terminals (end of the red lines) in the diagram below. [ http://i48.tinypic.com/eikbl.jpg ] F: If you do not have any voltage at ANY of the relay terminals OR just one of the terminals, then there is a break/open in the circuit that provides power TO the relay, possibly one of the fuses by the battery in pictured above in green, and the lines in red. G: If you DO have voltage the relay plug, and you know you have a good relay but STILL no voltage at the coils, it is possible there is a fault in the orange wire to the ECU pictured above causing the coil in the relay to not ground and not close the contact circuit of the relay. H: If you DO hear the relay click, but still no power at the coils, check the wires in yellow.
6. Bad ground wires/connections to the coils:
A: If you have continuity tested the PTU, cleaned the PTU connections, cleaned the CAS connections, and you DO HEAR the injectors click when turning the CAS then, B: Test for 12v at the middle terminal of the coil pack connectors harness side, and put the negative probe on smaller black wire at the coil pack connectors here. Put the negative test probe on the green arrow, and the positive test probe on the red arrow. [ http://i47.tinypic.com/es2knd.jpg ] C: If the ground circuit is good you will read 12v when testing this way, D: Or you can continuity test that smaller black wire (green arrow) with ground and measure the resistance (ohms) it should read perfect continuity or very close to zero ohms. E: If not, then either a ground isn't connected, or there is a break in the wire from the coils to ground, or dirty/corroded/loose connections. 7. Bad ground wires to the PTU: A: If you have checked everything just listed and it all checks out then, B: Test for continuity/resistance (ohms) at the ground wire to the PTU. c: As I stated before the PTU is grounded via the black wire going to the PTU on the side that has the 7 wires coming from it Pictured below. (where the green arrow is pointing) [ http://i50.tinypic.com/2lm43ye.jpg ] D: On the black plastic (new style) ptu's, the ground wire is the black one in the middle, I think it is on the side on the grey metal (old style) PTU's. Not 100% though. E: Turn your multi-meter to the resistance or ohms testing mode, and test the end of that black wire (green arrow) with body/engine/plenum ground and check it for resistance/continuity. You should have perfect continuity or very close to zero ohms. F: If not, then either one of your grounds isn't connected, there is a break in the wire from the PTU to ground connections, or loose/dirty/corroded ground connectors. 8. Break/open in the wires from PTU to the coils: A: If you have check everything else above and it all checks out, there may be open/broken wire from the PTU to the coils. Illustrated by the red arrow in the pic above, and the yellow arrow pictured below. [ http://i47.tinypic.com/es2knd.jpg ] B: To test, simply disconnect both the PTU and the connectors to the coil packs. C: Then using your multi-meter, test for continuity/resistance in ohms from the colored wire at the coil pack connectors pictured here (usually red with a colored stripe) and the corresponding wire at the PTU connector. There are numbers on the PTU that correspond to each cylinder. (E1 for cylinder 1 etc.) D: You should have perfect continuity or zero ohms of resistance, E: If you DO NOT have any continuity, remove the sub harness and test again to remove the subharness as a variable. F: If you DO have continuity AFTER disconnecting the subharness then the connection from the subharness to the wires that go to the coils is likely at fault. Clean the connections from the subharness to the coil pack wires, make sure they are tight, and try again. G: If you DO NOT have continuity either way, then there is a fault in the wires that run from the subharness to the coil pack connectors. 9. Break/open in the wires from the ECU to the PTU. A: If you have checked everything above and it all checks out good, then you may have a fault in the wires/connections from the ECU to the PTU. B: To test, disconnect the PTU and the ECU (REMOVE BATTERY POWER BEFORE DISCONNECTING ECU!! VERY IMPORTANT!!) C: Then use your multi-meter and test for continuity from the PTU wires from the ECU and the corresponding ECU terminal pins. Here is a picture of the ECU pin out. Make sure you translate the pin out to match which way you are looking at the ECU connector/harness. Test both through the subharness, and without the subharness. Follow the wires from the PTU to find out which wires go to which ECU pin. (I1 should be for cylinder 1 etc.) [ http://i45.tinypic.com/54ww91.jpg ] D: Again you should have perfect continuity or very close to zero ohms of resistance. E: If that all checks out fine, then there may be an issue with either a loose connection at the ECU connector/harness to the ECU itself. (as it was in my case when I just could not figure out why my #1 coil pack wasn't firing) F: Or a loose connection to or from the PTU or loose connection to the actual coil pack itself. If you have done everything on this page that I have listed and STILL don't have any spark then you have me stumped. Reply to this thread or just PM me and ill try to help you figure it out. __________________________________________________________________________________________________ JUST ONE COIL NOT FIRING. On a side note, if just one coil pack is not firing, it could just a bad coil or some of the things listed above. You can easily ohm test the coil by looking at page 179 of the EF and EC section of the FSM. pictured here. A. Try swapping out one of the other known good coil packs. If that doesn't work then check the things listed above. B. For me, my #1 coil wasn't firing and I could NOT figure out why for the longest time. It passed ALL the tests listed
above. C. One day I came up with the great idea of jumping the signal to fire from the #2 coil and jump it to the #1 coil since
I knew that the #2 coil circuit worked. D. I did this by disconnecting the connector at the subharness FROM the PTU to the coil wires, and sticking a wire FROM the #2 coil signal wire from the PTU and jumping it over to the #1 signal wire to the coils. Note: depending on where you break the circuit, you may need to also jumper the ground wire. E. I left the connector disconnected except for the jumper wire, and spun the CAS and SURE ENOUGH!! I Finally had spark!! this told me that the wires from the subharness to coil wires connector and the coil wires themselves were good, F. I then just started working my way back towards the PTU, by reconnecting the subharness to coil wires connector, and disconnecting the connector FROM the PTU to the coils/subharness, testing through the subharness. G. And again I had spark, I then did this at the subharness connector FROM the ECU and the PTU itself, and I again had spark, this told me that the #1 coil circuit in the PTU and wires to the coils and subharness was good. H. Lastly I jumped the connection at the wires from the ECU to the subharness from the ECU to PTU and again had spark. This told me that the wires from the coil to the subharness to the ptu and the subharness to the ECU connector was good. I. I then figured that the only thing it could be was a loose connection and the ECU harness, wiggled it a bit, took it off and put it back on a few times, and now I consistently have spark on ALL CYLINDERS!! YAY FINALLY!! __________________________________________________________________________________________________ I would also like to add some other basic pointers, If you have spark on some cylinders or not all, you can try swapping the coil packs around to see if it is a problem with the coil pack or the wiring to it. for example: Lets say, coil pack #1 is NOT firing, but #2 IS firing. You can swap the #1 and #2 coil packs around and see if the problem follows the coil packs or not. If you swap them around and now #2 is NOT firing, but #1 IS now firing. Then it is probably a bad coil pack or occasionally loose connectors to the coil pack itself. If you swap them around and NO change, ex: #1 still is NOT firing, and #2 still IS firing, then the coil pack is obviously good, because it is now firing on the #2 connector. This tells you that your problem is with the wiring to the coil pack, not the coil pack itself. IMPORTANT NOTE: ALL INJECTORS OR COIL PACKS FIRING AT ONCE. I also discovered that if the ground wire that is on the #6 coil pack bracket not properly grounded, ALL COILS WILL FIRE AT THE SAME TIME causing the PTU get EXTREMELY hot and will become permanently damaged if continued. Through someone with an issue with ALL INJECTORS FIRING AT THE SAME TIME, I suggested to check that specific ground connector on the #6 coil pack bracket and apparently that is what caused all of his injectors to fire at the same time.
Again, if you still have any issues, feel free to PM me or respond to this thread, and I will do whatever I can to help ;)
by Mario O. disclaimer: again I assume NO responsibility for any accidents/injuries/ or damage caused by any of these techniques. again I am usually on 300zxclub most of the time so pm'ing me there would be the best way to get a hold of me. Screen name is supermario680 here is the original thread at 3zc with working links and images [ http://www.300zxclub.com/showthread.php?p=1965559#post1965559 ]
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