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Matt, Mechanical Engineer
Category: Toyota
Satisfied Customers: 20361
Experience:  BEng, Repaired my own cars and others for 20 years, worked in Formula 1 for 10 years
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Sienna won't start. Battery, alternator, and started tested

Customer Question

Sienna won't start. Battery, alternator, and started tested fine. Tried new starter relay and that did not work.
JA: Does the engine turn over? How old is the battery?
Customer: No the engine does not turn over. Battery checks fine. Was lights, radio and AC work. Was able to jump it once and it started but now a jump does not work
JA: Are you hoping to fix this yourself?
Customer: yes
JA: Great! What have you tried so far?
Customer: starter relay
JA: Is there anything else important you think the Toyota Mechanic should know about your Toyota?
Customer: when you turn the key there is no clicking or anything from the engine
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Toyota Mechanic about your situation and then connect you two.
Submitted: 4 months ago.
Category: Toyota
Expert:  Matt replied 4 months ago.


If the car's not cranking then first check it can turned over by hand so double checking for any mechanical issues

If OK then 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

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

one other thing to consider is that the immobiliser is faulty and preventing the starter from being enabled - however if the dash / ignition lights are on then this usually means that its off

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

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