2 cylinders, code 13, 21.

[newtonty]

My silvia has been giving me problems ever since it bogged out on the side of the road. it was sputtering and sounding strange on the highway, then it would work fine. and all of a sudden it started dying between shifts (it did this before but only for one shift) so i pulled over, even though the temp gauge was around the middle the coolant in the overflow was boiling (engine was recently rebuilt and coolant was a bit low) so i trailered the car home, tested every wire for resistance, everything seems good. so i tested my ignitor chip, failed. bought a new one, did not fix the problem. So i decided to try diagnostics on my ECU, the screw was broken. after borrowing a known working ECU i started it, then shut it off and put it into diag mode. first code, 1 long beep 3 short beeps. 13, coolant temp sensor. so i tested that found it wasn't getting a ground, after fixing that it i reset the codes and it was still throwing a 13 (i did test the G/Y wire back for continuity from the plug on the harness to the ecu plug it is good). time to address the other problem, a code 21, ignition signal. this was a tough one as i've already tested all the ignition signals. so i double checked the ignition signals. bolted down my ignitor chip, and tested one of the bolt holes for ground (i can only get one bolt in.) the ignitor chip is grounded. could this be due to the ECU case NOT being bolted down? i've read about that causing problems but when this problem first occured the ecu was mounted. The car is currently running, but rough. either 2 or 3 cylinders, after the first time it died it was on 2, then 1 cyl for a little while. the first time it ever started having this problem was after the rebuild, it ran fine. but was ticking because the engine was upside down, so i bled the lifters (I did not remove the cam gears or really even remove the cam shafts. I undid the caps and was able to remove the lifters without removing the camshafts. I DID torque them to spec, and in sequence) started it up, 2 cylinders but the beautiful sound of no ticks. moved the coil packs a bit and started it up again, still 2 cylinders. moved them while it was running, bam started running perfect. so my question is, do the coilpacks ground threw themselves? i bought the car and the coil packs were not bolted down, i notice they have metal around the bolt hole like the ignitor chip. I have run out of ideas on what could be wrong. does anyone have experience with these codes? thank you in advance for your help I have searched and searched done almost all the tests in the FSM. The CAS plug has a small cut in the black/white striped wire. you can see the wire inside, but after searching all day today just for a ECU pin with no luck, i do not want to try to search for this pin.

[compactfean]

If your worried about that cas wire it should be cas power, just check the plug for 12 v with ign on. Id 12v exists than you should be fine. Your coolant temp sensor shouldnt be grounded I don't think. There should be 5v on one wire with ign on and the other wire is the signal wire to the ecu (which it sounds like you checked already but id have to double check an ecu pinout) your coils DO NOT need to be bolted down to work however if they aren't held down by anything its possible for the spring inside to nor make contact. Also use electrical tape and tape the boots on the coils, I've seen boots leak spark through them causing a misfire. The igniter chip doesn't need to be grounded, it has is own ground wire (check continuity to chassis, its the black wire) as far as code 21 I almost want to charge you for this answer! Lol, there are 2 blue/red stripe wires when doing the wiring for the swap in the plugs by the battery. The small one powers the igniter chip and in EVERY wiring install how.to, does not address this. The small blue/red wire must have 12v switched or you will always have code 21! In the fsm it says to check the blue/red wire but when there are 2 and the bigger one checks out fine you move on to the next step right? Lol. Took my like 10 months of searching the forums and looking at every how to and hours and hours of diag time, but that's deejay fixed my code 21. Btw the common grounding area for all of the engine sensors is the grounds that get booked to the intake manifold. Then the main ground from manifold to the chassis. Id both are good, id say you should be fine.

[newtonty]

I didn't wire in the swap, however it is a nissan silvia. so there was no modification of the SR harness needed, the car was running and driving. before this happened the car was running fine, i've read about people getting a code 21 from not having their coilpacks bolted down since the vibration of even just starting the engine can cause it to lose contact and throw a 21. but with the coolant temp signal, it wires into the signal ground. (i noticed mine was cut off at the ECU for some strange reason) It is only a resistor that changes from heat, so of course it needs to be grounded.

[compactfean]

Well yeah any sensor needs to be grounded somehow but the cts is not directly grounded to chassis. The ”ground” is the ecu reading it, then grounding it. Look at pin 18 in this diagram.

I couldnt find where the power comes from (maybe I was mistaken and its 12v?) But if you don't have voltage on the other wire the sensor will never work. I can assure a loose coil throwing code 21 had one of the other problems, no power to igniter, igniter ground wire poor continuity, even coil harness not grounded. I've checked for spark with the coil completely removed and plug not grounded yet and never thew a code 21.

[newtonty]

You are correct with 5V, the ground for the coolant temp sensor is "signal ground" which is what i tested it too, and i did look at the diagram. i'm almost certain that pin 18 sends 5V out through the sensor, and into the sensor ground measuring the resistance.