Replacement engine did not start, could it be the ECU?

LOZZ

MEMBER
2005 NISSAN MICRA
4 CYL
FWD
MANUAL

I've just put a second hand engine into it, it was just a block, head and sump so all my auxiliaries had to be put onto it, when it was finished it didn't want to start. So they went through all connections etc and plugged it in, it came back with Crankshaft Sensor, if it is unplugged the engine will run but with no guts, the sensor came of my old engine and before it came of the engine I never had this problem. Could this be correct or could it be something else like ECU?

1 Reply

JACOBANDNICKOLAS

MECHANIC
109,645 POSTS

Hi,

There is a chance it is the sensor or a wiring issue. When you disconnect the sensor, the computer goes into a default setting. This is to keep the engine running so you can get off the road or to a safe place. So, the first thing I would suggest is to check the crankshaft sensor and the wiring to it. Since the engine was replaced, there is a good chance the wiring or connector was damaged.

If you look through this link, it explains the common symptoms of a bad crankshaft position sensor. See if it seems to mirror what you experience.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

If possible, have the shop inspect the sensor itself. If the sensor is disconnected, there will be two pins in the sensor. All that is needed is a voltmeter or multimeter. Have a helper crank the engine to see if there is a pulsing voltage signal from the sensor. Note: Make sure to keep your hands and clothing away from moving parts.

I hope this helps. Let me know if you have other questions.

Take care,

Joe