How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Matt Your Own Question
Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 21726
Experience:  BEng hons Mech engineering, in auto industry 22 years
12772297
Type Your Car Question Here...
Matt is online now

engine malfunction light on and engine wont crank over and

Customer Question

engine malfunction light on and engine wont crank over and no diagnostic comuniction with e c u
Submitted: 2 years ago.
Category: Car
Expert:  Matt replied 2 years ago.

Hello

If the car's not cranking then first check that the main battery cables are on tight and the terminals are clean and bright. Do the same for the engine / gearbox earth strap.
Then follow the main positive lead back to the engine and down to the starter motor, and check the connection at this end as well.

There should also be a small wire to the motor which should have 12V when you're turning the ignition switch to crank. If the 12V isn't there, check back along this wire for damage to the insulation or corroded connections

if the battery is good and the dash isn't lighting up then its quite likely to be an immobilser issue

This 12V feed comes directly from the ignition switch so this may be faulty and need replacing

Check the resistance of the main positive lead that runs down to the motor as anything more than a few ohms and it should be replaced

Don't forget to try a jump start from another car / battery as its possible the battery is poor, if you have a voltmeter a healthy battery should read 12.7+V

also try substituting the battery for another as I've known a very flat battery to drag down the system voltage too far even with jump cables

If this is all OK then its possible the car needs a new starter motor