1994 Lexus LS400 has intermittent no spark. replaced ignitors, verified crankshaft position sensor resistance between terminals is within specification, verified ignition coils are good and receiving signal. temperature of vehicle does not effect this problem either way. It has spark, starts, and runs intermittently. When not running it is because of no spark. Anything else to check before assuming I must replace the ECU?

Intermittent ignition is usually caused by a weak crankshaft position sensor signal. Check for proper installation and inspect wiring and connector. Turn the key on and check the voltage on the third terminal. This should be 5 volts dc. Also check the other terminals as stated below.
TESTING

On the 2.5L engine, the Crankshaft Position (CMK) sensor is located near the outer edge of the flywheel (or starter ring gear). On other models it is fitted to the right side of the engine block.
The only test you can perform without a DRBII scan tool, or equivalent, is a basic check of the sensor only.

1. Disconnect the sensor harness connector from the main wire harness connector.
2. Place an ohmmeter across terminals 1 and 2 (see the illustration). The meter reading should be open (infinite resistance). If a low resistance is read, replace the camshaft position sensor.

There is really nothing to clean, unless you find sludge on it.

Camshaft Position (CMP) Sensor

OPERATION The Camshaft Position Sensor, or CMP sensor is located inside the distributor. The PCM uses the CMP signal to determine the position of the No. 1 cylinder piston during its power stroke. The PCM uses this information in conjunction with the crankshaft position sensor to determine spark timing among other things.
The CMP sensor contains a Hall effect device which sends either a 0.0 volt or a 5.0 volt signal to the PCM depending on the position of the distributor shaft.
If the cam signal is lost while the engine is running, the PCM will calculate spark timing based on the last CMP signal and the engine will continue to run. However, the engine will not run after it is shut off.


Fig. 1: Exploded view of a common camshaft position sensor and related components-1996 5.2L engine shown

TESTING

1. Make sure that the ignition is OFF , remove the distributor cap and turn the engine over by hand.
2. Verify that the distributor shaft turns. If the distributor shaft does not turn, the engine must be checked for proper mechanical operation.
3. Backprobe with a high impedance ohmmeter between the CMP sensor connector middle terminal and battery ground.
4. Verify that the resistance is less than 5 ohms. If the resistance is not as specified, repair or replace the wiring as necessary and continue the test.
5. With the ignition ON and the engine OFF , backprobe with a high impedance voltmeter between the sensor connector middle terminal and either of the end terminals.
6. Verify that a 5 volt or greater signal is present at one of the two terminals. If not as specified, repair or replace the wiring as necessary and continue the test.
7. With the ignition ON and the engine OFF , backprobe with a high impedance voltmeter between the sensor connector middle terminal and the end terminal that did not have the 5 volt or greater signal.
8. Crank the engine by hand and verify that the voltage reading alternates between 0.0 or 5.0 volts.
9. Install the distributor cap and crank the engine with starter. Verify that the voltage reading is 2.5 volts (averaging voltmeters only).
10. If the voltage readings are not as specified, the sensor may be faulty.

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Replace the crankshaft position sensor and you should be up and running like normal. Verify that there is no power or ground problem to the crankshaft sensor, the Yellow/Black wire should have battery voltage any time the key is on and the main relay is energized.Verify that the Brown/Yellow wire has a good ground. If all is good then replace.


P0335 - Crankshaft Position Sensor A Circuit Malfunction
The crankshaft position sensor (CKP) measures crankshaft location and relays this information to the PCM (Powertrain Control Module). Depending on the vehicle, the PCM uses this crankshaft position information to time the spark properly or on some systems it is only for misfire detection and does not control spark timing. The CKP sensor is stationary and works in harmony with a reluctor ring (or toothed ring) that is attached to the crankshaft. As this reluctor ring passes in front of the CKP sensor, the magnetic field created by the CKP sensor is interrupted and this creates a square wave voltage signal that the PCM interprets as crankshaft position. If the PCM detects that there are no crankshaft pulses or if it sees a problem with the pulses on the output circuit, P0335 will set.

Symptoms:
NOTE: If the crank sensor is used only for misfire detection and NOT spark timing (this varies with the vehicle), the vehicle should start and run with MIL (Malfunction indicator lamp) illumination. Also, some vehicles require several key cycles to illuminate the MIL. If this is the case, there may be no MIL illumination until the problem often enough over time. If the crank sensor is used for BOTH misfire detection and spark timing, the vehicle may or may not start. Symptoms may include:
Vehicle may not start (see above)
Vehicle may run rough or misfire
MIL illumination


A P0335 "check engine light" code could be caused by:
Damaged CKP sensor connector
Damaged reluctor ring (missing teeth or not turning due to sheared-off keyway)
Sensor output open
Sensor output shorted to ground
Sensor output shorted to voltage
Failed crank sensor
Broken timing belt
Failed PCM

Possible Solutions:
Using a scan tool, check if, when engine is running or cranking, that there is an RPM signal.
If there is no RPM reading, then visually inspect the crank sensor and connector for any damage and repair as necessary. If there is no visible damage, and you have access to a scope, you could check the CKP 5 Volt square wave pattern. If you do not, then, obtain a resistance reading of your crank sensor from a repair manual. (There are so many different types of crank sensors that there's no way to put here which resistance reading is correct). Then check the resistance of the CKP sensor by disconnecting the sensor and measuring resistance of the sensor. (It is best to check resistance readings from the PCM connector. This rules out any wiring problems from the start. But it does require some mechanical skill and shouldn't be performed if you\'re not familiar with automobile electrical systems). Is the sensor within resistance specs?
If not, replace the CKP sensor. If so, recheck resistance reading from the PCM connector. Is the reading still okay?
If not, repair open or short in the wiring to the crank sensor and re-check. If the reading is okay, the problem is intermittent or the PCM may be at fault. Try reconnecting and checking for RPM signal again. If there is now an RPM signal, wiggle test the wiring harness to try and induce the fault.

This code is basically identical to P0385. This code P0335 refers to Crankshaft Posistion Sensor "A", whereas P0385 refers to Crankshaft Position Sensor "B". Other crank sensor codes include P0016, P0017, P0018, P0019, P0335, P0336, P0337, P0338, P0339, P0385, P0386, P0387, P0388, and P0389.


Hope helps.

Hi, it can be either of those or possibly a shorted condense or a bad crank sensor. First, I would check for battery voltage at the positive terminals of the coil when the key is on. If no voltage there, try disconnecting the condenser. If there is voltage, then check for AC voltage across the coil terminals while cranking the engine. If there is no AC voltage, the problem may be the crankshaft position sensor. The crankshaft position sensor is located next to the flywheel/torque converter. The computer is rarely the problem unless there was a short that caused undue current to flow.




Testing Crankshaft Position Sensor
2.4L Engine

1. Disconnect the sensor electrical connector. Connect an ohmmeter.
2. Measure the resistance between terminals 2 and 3, on the crankshaft position side of the connector. Specification should be 0.486-0.594 kohm at 68 degrees F.
3. If measured value is not within specification, replace the sensor.

1. Be sure that the CKPS and PCM connectors are connected.
2. Engine ON and monitor the signal waveform of the sensor on the scan tool. Check whether the waveform is synchronized with the crankshaft position sensor or not.
3. If the waveform signal is normal, substitute with a known good PCM and check for proper operation. If the problem is corrected replace the PCM.
4. If the waveform signal is not normal, substitute with a known good CMPS sensor and check for proper operation. If the problem is corrected replace the CMPS.

2.5L Engines

1. Disconnect the sensor electrical connector. Connect an ohmmeter.
2. Measure the resistance between terminals 2 and 3, on the crankshaft position side of the connector. Specification should be 0.486-0.594 kohm at 68 degrees F.
3. If measured value is not within specification, replace the sensor.

Test the crankshatt position sensor. If it tests good, please get back to us.

OPERATION The Crankshaft Position (CKP) sensor provides a signal through the ignition module which the ECM uses as a reference to calculate rpm and crankshaft position.

TESTING The crankshaft sensor should be tested either cold 14-122°F (-10-50°C) or hot at 122-212°F (50-100°C).

1. Using an ohmmeter, measure the resistance between terminals. Resistance cold should read 1630-2740 ohms and hot; 2060-3225 ohms.
2. If resistance is not within specification, the sensor may be faulty.

REMOVAL & INSTALLATION See Figure 1

Fig. Fig. 1: The crankshaft position sensor is located to the right of the water pump-1MZ-FE engine

1. Disconnect the negative battery cable.
2. Remove the right hand engine under cover.
3. Remove the right side fender apron seal.
4. Remove the sensor wiring retaining nuts.
5. Remove the bolt and disconnect the crankshaft position sensor wiring, then withdraw the sensor.

To install:

1. Install the sensor and secure with the bolt to 69 inch lbs. (8 Nm).
2. Attach the engine wiring.
3. Install the right hand fender apron seal.
4. Install the right hand engine under cover.
5. Connect the negative battery cable.
6. Reset any electrical components such as the radio or clock.

P0016 is crank and cam out of sync.

TESTING

1. Disconnect the crankshaft position sensor wire harness plug.
2. Connect an ohmmeter to the sensor terminals A and B and measure the resistance. Fig. 1: Crankshaft position sensor connector terminals. Measure the resistance across the A and B terminals
   Fig. 2: Measure the air gap between the crankshaft position sensor and the crankshaft pulley
   
   
3. The reading should be 520–580 ohms at 68°F (20°C).
4. If not as specified, replace the sensor.
5. Measure the air gap of the sensor between the crankshaft pulley and the sensor.
6. Proper air gap should be 0.040–0.080 in. (1–2 mm).
7. If not as specified, inspect the crankshaft pulley and/or replace the sensor.

Ceck the ignition cam sensor must be in proper position with the cam gear.

TRY THE THROTTLE BODY POS SEN AND THE COMP