When you tried to jump-start the Pilot, did you connect the negative jumper-cable clamp to the battery post, or to a separate ground point? If to the battery clamp, try connecting directly to the chassis or engine instead, bypassing the little ground cable and connections completely.

A properly charged wet-cell car battery offers about 12.6V at rest. Engine running, expect between about 13.5 and almost 15 with engine running and charging. You don't mention how you measured yours.

In my opinion and experience, the little ground wire from battery negative post to chassis is a poor design. Cheap to manufacture and install, but... The wire in that cable is exposed at both ends where it's crimped, so subject to corrosion in there from battery fumes whenever it's charging. On the connection at the front bulkhead, all the current passes from the lug to the bolt, then the bolt to the threads in the threaded weldment there. The paint on the bulkhead blocks current flow across that contact surface, so the lug faces and the hole the bolt passes through must be shiny clean and bright. Ditto the bolt itself and the threads in the weldment. On the clamp to the post, it's a tin-plated copper ring formed out of sheet, and is at risk of poor connection from corrosion plus it can distort and actually lose contact if overtightened. The only recovery path is replacement with new if it's bee overtightened. Or it's corroded inside the insulation.

Last time I looked this cable was under $30 from Honda. If you shop the aftermarket, the new cable must have a lug that matches the original so it connects the bulkhead correctly.

 

I had similar symptoms when my starter failed. I tapped it with the lug wrench a few times and then it started right up.

 

@mclasser has a good tip. Tap the starter with a hammer or wrench, then try to start. If it works, that’s proof that it’s worn out. The solenoid connections inside wear down and become intermittent. The tapping trick works for a while, so get it replaced soon.

 

Thanks everyone. Dr Bob, to answer your questions -- when we tried to jump it, we connected the negative jumper cable to a separate ground point, not the negative battery terminal on the Pilot. And the multimeter reading on the battery was taken at rest, car not running.

I've been reading/watching more videos about this. When we try to start, we hear the fuel pump run, and we hear a definite click coming from the starter. (I even felt the starter with my hand while my son turned the key just to confirm that was indeed where the click was coming from.) I take this to mean the starter is in fact getting power from the battery. I read elsewhere about the trick of tapping/hammering the starter while trying to start the car, but unfortunately that hasn't worked for me.

So ... I'm at a loss. If the starter is getting power but not actually able to start the engine, does that confirm the starter is definitely the problem? Or could it still be something else, e.g., the alternator? (When we try to start, the check engine and battery lights on the dash come on and stay on.)

I'm warming to the idea of spending the $ on an OEM starter and attempting to replace it myself -- IF I can confirm that's really the issue.

 

Remove the starter and bench test it. That gets rid of other possibilities like bad cables, bad ground, bad relay etc.

Its just you and the starter.

 

Try @STMech's method if you want to pull the starter out for the test. Maybe before doing that...

For grins, connect your DMM to ground and the battery cable connection at the starter. Voltage there must stay above about 10VDC during cranking, assuming it's actually cranking. The starter solenoid gets the 'start' signal via the 50 terminal on the solenoid, and that draws the solenoid plunger in. Once that solenoid has the drive engaged, terminals at the back of the plunger close and the starter motor spins. You should hear the 'clunk' as the solenoid is drawn back, then the starter motor.

Battery and cable problems typically close the solenoid contacts OK, but the voltage drops at the battery cable contact on the on the solenoid. You hear clunk as the solenoid core is drawn back but voltage drops due to the poor cable/connection. With high voltage drop (more contacts resistance or weaker battery) the solenoid will chatter/buzz as voltage drops below the solenoid draw-in threshold. Whether battery terminal post (not clamps) voltage holds up helps define the cause -- battery post voltage drop means a weak undercharged damaged battery. High at the post and low at the solenoid terminal while cranking or trying says weak connections/cables.

 

I'd wager it's probably the starter. I highly doubt this is your issue but you'd also want to make sure the engine can turn and isn't seized. If you can't rotate the engine by hand, the starter sure as hell won't be able to.

 

Thanks everyone. Just to close the loop on this -- took it to a mechanic and it was indeed the starter.

 

Sorry was late to the party here.
Poor ground connection can cause this symptom.
I would have said to continue testing the continuity at each ground connection. With the voltage meter you had a 12.8v reading between battery posts. While leaving the positive lead on the positive post, move negative lead to where the battery terminal cable bolts to chassis. The number should not drop. If it drops try loosening and tightening 10mm bolt to chassis to create a clean connection. The cable may need replacing. Once voltage is restored at this connection, move the negative lead to the ground wire connection to starter. If the voltage drops, clean connections and replace ground strap from starter to chassis if needed. 12.8 voltage should remain on the engine and transmission. If any of these had a drop, also test the transmission ground strap. It is likely providing poor continuity too.
Glad your fixed and going.