496HO TPS low range?
 

Hi guys!

I just did a pre-startup test on my engines for the weekends startup.

I just put the ignition on and tested to see if they ware able to crank. They did crank but after 0,5 sec I got an an alarm from my Smartcraft system saying TPS low range on stb engine.

I know this is the throttle position sensor, but is it dangerous to start her up in the weekend anyway? I just tested to crank her for 0,5 sec to see before I take her out of the garage. Could this error code be just that I didnt fully crank her?

I will check for loose connections and corrosion but I doubt it.

Please give me some feedback about this, it dosent seem to be that common..

From the PCM diagnostics manual:
Go ahead and start it and see if it gives the same error code.

Thanks, Ill test this weekend!

Everything was working fine when I took her out of the water in Oktober so I dont think there is any misadjusted throttle linkage..

Is there a manual online for the smartcraft system? Can i check the engine with it the same way as Rinda scan tool? Cant find any reset error code...

Hi again, I need help!

Ive tested to move the TPS sensor from stb to port and the other way around, smartcraft still complains on low range TPS on stb side? That would rule out a bad sensor I guess?

And now I also get engine fault critical on both starboard and port engine?

Is there a way to get more info out of the smartcraft or do I need to hook up a scantool?

Scan it, with all the electronics on modern motors you will be chasing your tail for days.

But will I see something different from what I see in the Smartcraft? Isint that the same system?

Much more info is available on the scan tool . The actual TPS output voltage for one. The manual states it should be .7 volts at idle and 4.5 Volts at WOT.

Should i be able to measure that with a regular fluke? I live far off where the scanners are hard to find but Ill see if I can locate one.

BUT, after todays fail search, the engine fail alarm goes off when I turn the ignition on, and comes back when turn ignition off ( no problem just as it should be then)

The strange thing with the TPS sensor is that i I give the throttle for the port engine 1/2 gas then alarm stops?!

Port side works fine, if I move the sensor from port side to strb and vice verse the error stays the same, no matter of which sensor I use. I need to have the throttle at 1/2 on strb for the alarm to stop?

The throttle axles have the same position.

Conclusion: Sensor is ok.

Now what?

You could check the sensor with a fluke when the cap is not attached. It's a simple rheostat device.

The difficulty would be checking its operation while the cap is on. There's no easy access to the connections for using a fluke. You may be able to identify the correct pins on the computer connector however. They are easier to get to with a meter even when connected.

The cap and wire connections to the TPS may very well be the problem. They are fragile. My friend had a rough time tracking down a bad connnection to his seawater presure sensor cap on his 496.

Ok, but if I move the sensor to the port engine it works fine!

So there must be something else then the sensor?

Could be voltage drop during cranking.
Your batteries needs to be in good condition and have high CCA rating.

I have a new battery installed 2 weeks ago, with the proper rating.

And all this takes place with the engines off and only ignition on.

With the cap removed from the sensor and the ignition on, one pin on the sensor cap (not the sensor itself) should have a solid +5 Volts DC. It's the regulated DC sensor supply voltage from the computer. Another pin should be a soild connection to ground.

These could be checked with a Fluke meter.

Update of the situation,

Thanks to a stand up guy I could do some more fail search.

I have TPS low range on stbd and transducer low voltage (which is the grey reference voltage)

On strb I only have 0.36V on the grey cable that is the reference to the sensor. This goes for all the sensors. The blue cable only gives 0.24V with the throttle on idle and 0.35V on full.

I I take the sensor from port side I get the same result. => Not sensor related issue

I then swapped boxes, and the fault code follows the strb box to the port engine BUT
when I measure port sensor it shows 5V on grey and 0.5V to 4.6V on blue.
However strb grey cable voltage still remains at 0.36V

Or is the boxes programmed as port/strb? Thats why its saying port low range when its still stbd that has low voltage?

It sounds like the fault hasn't been cleared from the original stbd box and you have a wire harness or sensor cap problem with the stbd engine.

Does the strb engine still show a fault using the port box?

Stbd engine still only has 0.36V on the grey reference voltage cable.

Port engine has the right voltage on everything. But if I pull the working sensor from
port engine it says stbd engine tps fault. => The box is calibrated to stbd and port.

So boxes are ok. Why do I only get 0.36V on the grey in the whole system?

It seems The 5 volt reference voltage is not getting through your wiring harness on your stbd engine. That could be either an open connection in that line or a short circuit in another sensor pulling down that voltage (assuming it's correct comming out of the computer). Any of these problems can be tracked down using that voltmeter on the ohms function if you know how.

You are right!

I took out the grey cable from the multiconnector (disconnectsensors from the harnes sensor side)
Then I get 5V on the box side :)

Ive unconnected all the sensors i found but still no more voltage
in the harness. According to the scheme the grey cable splits up into
all the sensors - but where I thought that could be a good point to start from?

Or is it a better easier way to track down issue along the cable?

Disconnecting all the sensors is the right place to start. Are you sure you got them all? Seawater pump, port and stbd exhaust, crank position, IAC, manifold pressure. I can't think of any others but that 5 volts goes a lot of places. Unfortunately I don't have a schematic in front of me.

Try a resistance reading from the box end to each sensor with the ignnition off. Should be near 0 Ohms.

I got:
Seawater
Camshaft ( below the waterpump)
IAC (No grey cable here?)
MAP
TPS
ECT

Missed the exhaust sensor, also crank or is that the camshaft? Will try that tomorrow, now Ill just have to gain some knowledge in measuring, and collect a few more ideas on what to try next.

Do I have to remove the grey cable from the box to do the Ohm reading?

Thanks for the input Nighthawk, stand up guys on forums helping newbees like me is great and Im very thankful.

Not absolutely necessary but I would.

Newbee question, the cable is not short circuit due to having 0.36V thru
the whole harness. So if I test continuity, what will I found out?

You're looking for a possible high resistance such as might be caused by a corroded contact or broken/near broken wire. There should be 0 Ohms to maybe 2 Ohms max from the box end of the 5 volt circuit to every sensor grey wire connection.

Hmm.. I have 2 Ohms from all the connectors to the grey wire at the box. .
Also 2 Ohm between the grey and ground.

0.36 volt from grey to all the ground points i can find in the boat. .

Short circuit in the trim sender caused the 5V harness to malfunction.

Now everything is working as it should!

Thank you so much for the help!

That was the big clue. Good job, glad you found it. Everyone learns from this kind of stuff. The trim sender isn't connected to the computer on my boat. I wouldn't have guessed that.