I need help! I replaced the IAC on one of my engines a few weeks ago. That engine is now running fine, however the soft code...beep....beep is still there. I scanned the engine yesterday and the code I got was Main power relay output...code # 80. I'm assuming this could mean multiple things, but I'm having trouble finding anything specific to the mpr...any help is appreciated.

Could be anything...start with the obvious.
- Check your drive fluid reservoir level
- Check Cam position sensor
- Check the bundle of 4ea small 15/10a fuses on the tops of the engines. I know this sounds weird but there is a small bundle of 4 fuses in a single plug looking deal and I once chased a blown fuse there for over a week and it was showing as "power relay"
- Check relays located near this same bundle - pull off the engine cover should be right there on top. Check those relays. (swap from known good running engine if available before buying a replacement)
- Battery voltage and health check

If only there was a person.....nay....a Saint to 496 owners who could help? Will anyone here be able to fill the void left behind by BUP? Will anyone call out his name or provide insight with such detail and obsession to resolving this mans issues?

i am surprized BUP does not come up with a new screen name and spoof his ip address it is easier to do than reflashing a boat computer.............i love the guy that the home owners association made him take the trump flag off his boat so he renamed it and had it wrapped with a huge trump thats american spirit!

The manual says possible causes are Short in MPR circuit, Low battery voltage, Faulty MPR.

Would be very easy to tell it's him from the information/answers provided!

Isn't it more fun this way?
BUP would be asking for a serial number because he knows not all 496s are the same. And that this circuit changes at a serial number break.

What is a Main Power Relay (MPR) Output Fault?
If the battery voltage available at the engine is less than 7.5 volts, for example, during cranking, the MPR may not close or even remain closed during cranking, resulting in no spark, no injector activity, or no voltage to the electric fuel pump. The PCM decides the MPR output circuit is at fault and sets a fault code, which is stored in the Freeze Frame buffer. An MPR output fault can be one of three types: the voltage being transferred across its relay contacts is below allowable limits, the relay coil itself is faulty, or its connection to the relay coil socket or the associated harness wire is open circuit. Other typical problems that may cause MPR output faults:

== Incorrect battery type and capacity

== Use of a deep cycle battery as the primary cranking battery

== Loose or corroded battery cable connections (at the battery or the engine)

== Discharged battery (shorted or dead cells)

== Faulty battery switch contacts or loose connections

== Short extension wires from battery switches that have excessive amounts of shrink sleeve partially covering the ring terminals

== Incorrectly sized battery cables if longer battery cables are required
== 12‑volt power bus‑bar connection problem


It gets a bit trickier if it's an intermittent fault.

I would check the voltage at "A" and "B" which should be the same when engine is running. Engine off only "A" should have battery voltage.