QuestionWhile driving, my 1998 Hyundai Elantra will stop running without warning, no noise ect. Just as if I turned off the ignition. After sitting 20 minutes or so, I am able to start it and drive 2 to 3 miles before it happens again. The check engine light is on. Diagnostic codes are: P335 and PO727. I was advised that replacing the crankshaft positioning sensor would take care of both these codes and fix the problem. It was replaced but the problem remains. The check engine light is on and it is still stalling ect... What should I do next to repair my car?
AnswerHi, Jane. I'm very surprised that replacing the crank sensor did not repair this issue. Because of the stored codes, we know that the issue is that the ECM is not receiving a correct crank sensor signal. So we'll need to go back and check some things before doing anything else.
1. Check the old sensor for physical damage to the end that is inside the engine. Damage implies that the tone wheel on the crankshaft is loose or damaged, and you'll need major engine work.
2. Verify that the new sensor is installed properly. It should be fully inserted in the hole. Did the o-ring come out with the old sensor? If not, you may have two o-rings on the new sensor, causing it to be held too far away from the tone wheel on the crankshaft.
3. Remove the new crank sensor and insert a flat-blade screwdriver inside the hole so that it falls into one of the indentations in the tone wheel. Verify that you cannot move the wheel back and forth with the screwdriver. If you can, this indicates the wheel is loose, requiring major engine work to repair.
-- The rest of the tests need to be conducted while the engine will not run in order to be valid. Otherwise, they'll show good results regardless of whether what you're testing is the problem. In addition, you'll need a multimeter to run these tests.--
4. Unplug the crank sensor, and check the voltage between the black wire at the connector and the positive battery terminal. You should have battery voltage. If you do not, there is an open circuit in the ground circuit.
5. Check the voltage between the same wire and the negative battery terminal. The voltage should be less than 100mV. If not, there is excessive resistance in the ground circuit for the sensor.
-- Registering for a free account at www.hmaservice.com will be helpful for the next steps. The shop manual has information on the crank sensor, which includes a diagram of the ECM connector among other useful things. --
6. Disconnect the battery and unplug the ECM. Check the resistance between pin 16 (yellow wire) and pin 43 (brown wire). This should be 540 +/- 54 Ohms at 68 degrees F. So, presuming the engine is warm, I'd say up to 650 Ohms is probably still okay. If you have much higher than that, there's an open circuit or excessive resistance in one of the wires you're probing. If you have less than 486 Ohms, the sensor itself has insufficient resistance.
7. With the ECM still unplugged, check the resistance between one of the wires and a bare piece of metal behind the dash. There should be no continuity. If you have no resistance, the wire you're probing is shorted to ground somewhere between the ECM and the sensor. If the you have the same resistance as in the last step, the wire from which you removed the probe is shorted to ground somewhere.
If all the above tests have good results (while the engine will not run for tests 4 - 7), there are only two possibilities: a defective crank sensor or a defective ECM.
