MuGGzyx

I have seen info on how to test conventional coils for resistance with a regular multimeter but the coils on our cars are obviously not like the old beer can shaped types that you can just touch the outside and inside.

Is there a way to use a meter to test them or only the way that people have posted on here with, that being looking for arcs and sparks etc.

Ali SC3

iTrader: (10)

yes, you unplug the coil, there will be 2 prongs on the connector. check the resistance as stated in the manual.

MuGGzyx

I found this article on another Lexus forum and since I couldn't find the info here I figured I would post it for anyone else searching for this info in the future. Missing pics that are referenced (aka "see Fig 2") but still worthwhile.

IGNITION CHECKS
SPARK TEST

Remove coil wire from distributor. Using insulated pliers, hold end of coil wire 1/2" from ground. Crank engine. If spark is present, see appropriate DIAGNOSIS BY SYMPTOM in TESTS W/O CODES article in the ENGINE PERFORMANCE Section.
If spark is not present, turn ignition off. Check ignition coil, ignitor and distributor connectors. Repair as necessary.
If connectors are okay, check resistance of high tension cables. Maximum resistance is 25,000 ohms per cable. Replace as necessary. If resistance is within specification, go to next step.
Turn ignition on. Using a DVOM, ensure battery voltage is present at ignition coil positive terminal. If battery voltage is not present, check wiring between ignition switch and ignition coil. If battery voltage is present, go to next step.
NOTE:LS400 and SC400 have 2 ignition coils.

Turn ignition off. Using a DVOM, measure resistance of ignition coil (cold). Positive terminal on ignition coil has a tab next to terminal. See IGNITION COIL RESISTANCE table. If resistance is not within specification, replace ignition coil. If resistance is within specification, go to step 6) for ES300 and SC300 or step 9) for LS400 and SC400.
IGNITION COIL RESISTANCE
ApplicationPrimarySecondary
ES300.30-.609000-15,000
LS400 & SC400.40-.5010,200-13,800
SC300.20-.306000-11,000

On ES300 and SC300, measure resistance of pick-up coil. See Fig. 2 . See DISTRIBUTOR SENSOR RESISTANCE table. If resistance is not within specification, replace distributor housing assembly.
Check air gap in distributor. Measure air gap of G1 pick-up, G2 pick-up and NE pick-up. See Fig. 3 . Air gap specification for ES300 is .008-.020" (.2-.5 mm). Air gap specification for SC300 is .008-.016" (.2-.4 mm). If air gap is not to specification, replace distributor.
If air gap is to specification, perform appropriate trouble shooting procedures in TESTS W/CODES article in the ENGINE PERFORMANCE Section. If voltage reading and wiring harness are okay, substitute ignitor with a known good unit.
DISTRIBUTOR SENSOR RESISTANCE
ApplicationOhms
ES300 & SC300
Pick-Up Coils
Between Terminals G1 & G125-190
Between Terminals G2 & G125-190
Between Terminals NE & G155-240
LS400
No. 1 & No. 2 Cam Sensors950-1250
Engine Speed Sensor950-1250
SC400
No. 1 & No. 2 Cam Sensors835-1350
Engine Speed Sensor835-1350

Fig. 2: Identifying Pick-Up Coil Connectors (ES300 & SC300)
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
Fig. 3: Measuring Pick-Up Air Gap (ES300 & SC300)
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.
On LS400 and SC400 models, use an ohmmeter to measure resistance of No. 1 cam position sensor. See Fig. 4 . See DISTRIBUTOR SENSOR RESISTANCE table. If No. 1 cam position sensor resistance is not to specification, replace sensor. If resistance is within specification, go to next step.
Using an ohmmeter, measure resistance of No. 2 cam position sensor. See Fig. 5 . See DISTRIBUTOR SENSOR RESISTANCE table. If No. 2 cam position sensor resistance is not to specification, replace sensor. If resistance is within specification, go to next step.
Using an ohmmeter, measure resistance of engine speed sensor. See Fig. 6 . See DISTRIBUTOR SENSOR RESISTANCE table. If engine speed sensor resistance is not to specification, replace sensor. If resistance is within specification, perform appropriate diagnostic procedures for LS400 or SC400. See TESTS W/CODES article in the ENGINE PERFORMANCE Section.

MGa

iTrader: (1)

Bringing this old thread back to life.

My car is misfiring and I measured ignition coils and the primary resistance was 0.8 on the other one and 1.0 on the other. Does this mean they are both broken?
The manual says the value should be between 0.40-0.50.

I had a check engine light and code P0340 saying my camshaft position sensor was bad. I replaced the sensor with a used one and the ECU capacitors were also changed. Check engine light is not on anymore but car is misfiring and a lot when over 3krpm.

Edit. The car is non-vvti -97 SC400.

Ali SC3

iTrader: (10)

does it misfire below 3k rpm? its normal for it to be a little different than in the manual, resistance will go up and down depending on weather and if the coil is hot or cold. usually if one is a lot different than the other then you know one is bad, they both seem pretty close. usually also when they fail they stop working completely.

on the v8 there is a cam sensor wire coming out of the left cam cover that runs down the front of the engine, sometimes if there was a timing belt job and someone places the fan bracket back on without putting that wire behind the bracket, it will hang out too far infront of it and get chewed up by the serpentine belt. I only mention it cause you had a cam sensor code. dangle that wire and see if it misfires when you do that. other than that the timing being out of alignment could throw that code as well, like if something mechanical has gone wrong.

could be lots of things but just throwing those out there.

MGa

iTrader: (1)

Yes it misfires also below 3k, but over that it's really misfiring badly.

I measured the resistance with another multimeter and it was showing only 0.6ohms, so it's pretty close to factory specs.

I changed the drivers side(left) sensor, so I think the wire is ok. The car was standing for 4 months so I also added some fresh gas but that didn't help. Hmm I really have no idea where to start looking next.

Ali SC3

iTrader: (10)

if its the distributor style motor, then is could be caps and rotor also. those wear out over time.
you can try plugs and wires also for that sort of issue if they haven't been done in a while as well.

MGa

iTrader: (1)

Thanks for trying to help out Ali. I have replaced caps, rotors, spark plugs&wires 3 years ago and not many miles since that. Also have changed the alternator. And just now new battery.

Ali SC3

iTrader: (10)

at that point the next thing I would do is verify the engine hasn't moved out of timing.
remove the cam covers and check that the cams are lined up with the spot on the cover when the engine is at 0 degrees on the crank. its possible that a leaky waterpump or other factor caused the belt to slip on one of the cams. since the sensor is only on the drivers cam it wont know if the passenger side has jumped except it would run with a misfire. even if it isn't that then you can at least know its all still timed up.

MGa

iTrader: (1)

I was just thinking the same thing, have to check the timing.
Oh and by the way there are sensor on both cams. I have also replaced the ECU capacitors but that didn't fix the issue either.

MGa

iTrader: (1)

What do you think, has my timing belt skipped a teeth?
There is 9-10mm between the cam marks and the motor marks when the crank is at 0.