496 mag ho no start. Code 123 and 133
 

Looking for some help. I have a 2002 powerquest 340 Vyper with two 496 mag ho. The batteries were dead when I tried starting it a couple weeks ago and put the jumper cables and a jump box on it. The batteries are brand new they only went dead because I left the battery switch's on. Now starboard engine won't start. I plugged it into the scanner I get a TPS 123 code and a low voltage 133 code. I swapped PCMS with port, that didn't work. I swapped TPS sensors that didn't work. No breakers are tripped that I can tell. Does anybody know if there's a fuse panel somewhere? Or have any ideas?

Leaving the bat switch ON should not kill the battery, you have a heavy drain going on. What is the battery voltage with key OFF, then ON, then while cranking? Could be your alternator has shorted out if battery stays low

Do you have the proper service manuals to help with diagnostics ? so was power still on when you were changing out sensor(s) and the PCM. hopefully you did not put a known good pcm on the bad engine ??? HUGE MISTAKE to do that. You test the other way around - bad engine PCM on good motor - there is a reason for that keeping known good PCM's alive.

Also code 133 is NOT a fault code anyone thinks it is. Code 133 is the 5 V power low- Meaning this is the 5 V power that supplies all the sensors its 5V reference so that code actually means Excessive current draw on the 5 V circuit in return means sensor(s) and or the circuit shorted to ground. So whats unplug or shorted ?

Just asking is your app DTS ? I do not think it is but still a ?

So since 123 tps swnsos is the only other code does the lead you to believe the TPS wiring has a short or bad ground?

I will definitely check tomorrow . I unhooked battery and hooked back up to see lif that changed the pcm's mind about things .when I re hooked up battery pretty good arc meaning draw. My multimeter read 13.2 with the key off . Will try with it on .thank you

Disconnect the battery then, remove the orange wire from the alternator. Then reconnect the ALT and see if you still get the arc

Tried
 

Ok so I've unhooked alternator completely still have the draw spark on battery . Batteries 12.4v when I turn key on drops .2 volts crank starter drops to 10.5v
I do not have diagnostic manual. What sensor (s) are on 5 v system? If I unplugged one at a time and try it will I find the bad one? Or when sensor unplugged no start?
The dia. Scanner I have is not the laptop one just code reader .

make sure if you have bilge pump FLOAT switch that it is not discharging your batteries.

How about your stereo / amps and all that - possible discharging the batteries ? I would unhook these to see what happens if applicable.

something in the cabin running - fridge or lites - courtesy lites ??

QUOT

I did unhook sub and stereo amps. Shut off all breakers and power in the cabin. Still will not start just cranks and beeps while cranking. Leave key on and beep twice every 2 minutes

The spark with nothing on concerns me, maybe the battery charger

So far as the beeps, I would connect a meter to the 5V circuit, then start unplugging some of the sensors, water pressure, water temp, IAC, TPS and just turn ignition to ON. When the shorted sensor is unhooked, the voltage will go up to 5V

So close
 

Ok....so there's 3 wires in the plug that plug into the TPS sensor, a black/purple, a blue, and a grey. On the engine that runs test continuity on all 3 wires black/purple goes to ground, on blue and grey OL (open)
On engine that won't run the grey wire goes to ground. So where does grey wire go?

you will need to post both of engine serial numbers. many things change thru out the years with the 496 including the wiring harness. 10 pin went to a 14 pin harness. Also possible on your app one engine might be older than the other. --- I Have no idea unless I was looking at them and or run the engine serial numbers.

Also are the engines totally stock apps ??? If not what is the set up - in detailed info.

from the start of the 496 birth the that last production day end of the 496 Marine side - I prob can list over 100 different things how the 496 changed thru out the years. -- actually easily way over a 100 things changed for the 496 marine application thru out the years.

So my 496 mag ho is the 0M0000000. Today I checked ever PCM pin on both engines and the checked out the same EXCEPT 5 V on good engine and only 3 V on other for what I believe is the 5v system. The only other discrepancy is I have a ground on the good engine at TPS sensor (black and purple with) with the key on and no ground on same wire on bad engine

Short
 

So in my 5v system I have 3 volts on the 5 volt line and 2 volts on the ground line . Is it s sensor? Is it a bad ground?
If it was a short in a sensor wouldn't I have continuity on the 5v line to ground?

The "short" term is meant to indicate something is drawing enough current to drop the reference voltage below the standard or 5V in this case. Same goes with a starter motor and the battery. If the starter pulls more current when cranking the motor, voltage will drop further down. So there is something in the 5V circuit which is pulling more current then normal which is dropping the voltage to 3V, but is not a dea short which would pull down to 0V if not blow a fuse when doing so.

If it was a bad ground the voltage would show full 5V and there would be a code for the bad sensor for not providing the correct range voltage back to the ECM

So why is the 2 of my 5v in the ground line and 3v in the 5v grey line? Has to be a sensor right. Will a laptop program show which sensor is bad? Or will they all have funny readings because there's only 3v running through the system?

This is not real clear but I think your saying that 2 of the 5V lines are at 3V and others are at 5V?

If this is the case then there is either a break in the grey wire splice, or if they are all 3V then there is either one or more sensors drawing to much current.

The software is looking at info supplied by the ECM, and if all the Gray wires are low then it will say all sensors have bad readings (so to speak)

https://cimg7.ibsrv.net/gimg/www.off...81264973e4.jpg

Great info!
 

Yes all sensors I have found so far only have 3volts. TPS, map, the one going in outdrive, iac, crankshaft, Now I just have to find the rest if I can get to them. With that schematic I now know all 5v system sensors. When I unplugged the bad sensor I should get my 5volts back. Thank you so much for the info!

I replied to this on because it wouldn't let me reply to the picture post

If you're measuring that correctly only one thing can cause 2 volts on a ground line and that's a bad ground. Ground should be ground. I'd focus on that..

Or a short to ground in a sensor right? If sensor is bad it will put voltage in gound line

No, if the ground line is actually grounded properly no voltage is possible on that ground line, no matter what happens at the sensor. That's assuming the other lead of your meter is on a good ground point.

If it were me I would clean and reseat the connector at the PCM but that should ONLY be done by someone wearing an anti-static bracelet.

I keep thinking bad ground too. I've checked plug at pcm exactly the same (gounds, and power) as port engine on every reading .I put PCM of the engine that won't start on good engine I get 5volts as it should and it starts but not when I put it back on starboard. So it keeps leading me back to a bad sensor feeding 2volts into the ground wire through out the whole 5-volt system
I thought if it was a short to ground I would have some resistance in the 5v wires but, not seeing that either . Just 3v on grey wires at sensors I have checked and 2 volts on the black ground wire at respective plugs

The sensor can not feed 2 Volts into the ground wire if it's really grounded. If the ground wire connection is good then there should be 0 Ohms from the ground lead to wherever you are grounding your meter. It's impossible to measure 2 Volts across 0 Ohms.

If however there is bad connection, due to either corrosion or bad pin for example, then you might start to see more than 0 Ohms to ground and it will be possible to develop voltage at that point.

If you're sure the point where you're seeing 2 Volts is the ground connection, measure the resistance from that point to a known good ground with the ignition off. It should be no more than 0.2 Ohms.

AllDodge's diagram shows a +5V harness splice labeled 101. There's also a ground splice (100) in there somewhere. They're worth look at if you can find them.

A short circuit between the 5 v wiring to ground. Any external sensor and or accessory Smartcraft sensors if improperly connected / or however can overload the 5 V supply. Also anything that was spliced in on top of ---- that should not be there . Any Extra accessories ???.

easy testing is --- discount each sensor one at time until you see the constant 5 V supply.

Also disconnect the main smartcraft accessory harness to see if the voltage problem then corrects itself.

get rid of any spliced in whatever after the fact not from the OEM - including any stereo BS if it was. I have no idea without looking at it.

This is not that hard to fix at all with proper testing and tools. Possible seek out someone that is good with the 555 engines including myself. Good luck

Solved!!
 

If it's the first answer you come to on Google there's a good chance it's right. I did find the most common sensor to go is the water pressure sensor on the raw water pump. I unplugged the bad sensor and I got my 5 volts back at the TPS sensor. I pluplug the TPS sensor in and the engine fired right up.

Thank you for all who helped and problem solved with me. If you're ever in Canandaigua New York and want me to buy you a beer I'll buy all you can drink. Thanks so much!!

Great to know and super glad I posted another great testing tip that helped with the fix plus for whomever down the road. And I quote " EASY TESTING IS ---- DISCOUNT EACH SENSOR ONE AT A TIME UNTIL YOU SEE THE CONSTANT 5 V SUPPLY

Your the man