Can Potentiometer cause alarm?

[Tanner]

So I've eliminated everything I can think of that could cause an alarm and still get it when going in and out of gear.... just not in neutral. I was talking w/ Harvey the other day about my throttle being really sensitive and he mentioned my potentiometer is prob. bad. Can a bad potentiometer cause an alarm due to the throttle by wire?

Also what are the random chances that O'reilly's or Napa would have one?

[dom w. forte]

So I've eliminated everything I can think of that could cause an alarm and still get it when going in and out of gear.... just not in neutral. I was talking w/ Harvey the other day about my throttle being really sensitive and he mentioned my potentiometer is prob. bad. Can a bad potentiometer cause an alarm due to the throttle by wire?

Also what are the random chances that O'reilly's or Napa would have one?

Yes the throttle can cause an alarm and go into limp mode.
Need more data of complaint, and the sensor is only available through PCM .

[yearroundboarder]

Throttle Issues, Buzzer and Limp Mode

I was having throttle issues with my 2006 22Ve (Dual Batteries, 5.7 340HP MP); low RPM to Neutral was sounding alarm and limp mode. I had the TCM/ECU rewire done by TWS - didn't fix the problem, but the boat did run better. Still was getting the alarm and limp mode when I backed off the throttle to neutral. With help from Dom @ Fortes, I determined the next thing to look at was the potentiometer (bad or needed adjustment). I pulled the throttle, removed the potentiometer. What I found was a six-pin, rotary-style Industrial Position Sensor. TWS and Tige' were out of this part so I did some homework. To my suprise, it's made by BEI Sensors in Irvine, CA. Model #9861 is a standard part for them and can be bought through one of their distributors. I called Mouser Electronics (www.mouser.com) and orderd Part# 9861R5KL2.0 for $58.50/each. Mine was slighly more as I had it shipped FedEx Overnight. This took me only 15 minutes to install and adjust. Ran two full days this weekend with no more buzzer or limp mode. Not saying this is the magic bullet, but it did correct the problem for now. My guess is this may need to be replaced again, but it beats replacing the throttle assembly.

[Ewok]

Should this go sticky? I'll keep in mind down the road.

[bryanwmitchell]

I was having throttle issues with my 2006 22Ve (Dual Batteries, 5.7 340HP MP); low RPM to Neutral was sounding alarm and limp mode. I had the TCM/ECU rewire done by TWS - didn't fix the problem, but the boat did run better. Still was getting the alarm and limp mode when I backed off the throttle to neutral. With help from Dom @ Fortes, I determined the next thing to look at was the potentiometer (bad or needed adjustment). I pulled the throttle, removed the potentiometer. What I found was a six-pin, rotary-style Industrial Position Sensor. TWS and Tige' were out of this part so I did some homework. To my suprise, it's made by BEI Sensors in Irvine, CA. Model #9861 is a standard part for them and can be bought through one of their distributors. I called Mouser Electronics (www.mouser.com) and orderd Part# 9861R5KL2.0 for $58.50/each. Mine was slighly more as I had it shipped FedEx Overnight. This took me only 15 minutes to install and adjust. Ran two full days this weekend with no more buzzer or limp mode. Not saying this is the magic bullet, but it did correct the problem for now. My guess is this may need to be replaced again, but it beats replacing the throttle assembly.

I GOOGLED THE PART NUMBER AND FOUND ONE ON EBAY FOR $20 BUCKS AND $5 SHIPPING WILL LET EVERYONE KNOW AS SOON AS IT IS INSTALLED

[YVRGlen]

I am having the exact same issue with my 2006 22Ve. I am presently on holiday at a fairly remote lake and have ordered a potentiometer to the nearest town. If anyone can give me any tips on replacement or send a couple of pictures that would be greatly appreciated. Thanks from YVRGlen

[IDBoating]

In case anyone cares, here's some background on what is likely happening here.

That potentiometer is actually a DUAL potentiometer - that's why it has six terminals. Pots have three terminals: Two for the ends of the active element and one for the wiper.

Engine controllers accept signals from dual throttle position sensors as a safety feature. The two readings are supposed to be within a few percent of each other. If they vary outside of that tolerance range, the engine controller will generally restrict engine operation ("limp mode") because, frankly, it doesn't know which reading (if either!) is accurate and thus cannot safely decide how fast the engine should be operating.

In an emergency situation (I'm thinking being stranded on the open ocean), it might be possible to use just one of the two pots to provide a common signal to the ECU. But that would take some careful experimentation by someone who understands what is going on electrically, and I'd only do it in dire circumstances and only just long enough to get to safety.

In most electronics, pots (even duals) are relatively inexpensive items (example: when I reworked a swim meet starting system its pots cost about a buck each). But these are likely sealed units, "marine" or "automotive" grade, and carry a commensurate price premium. Also they probably have the correct physical mounting configuration. As an example, the TPS on my old Mercury V6 is a ~$300 part, and it is only a single pot! So while sixty bucks may feel like a lot, I promise it could be a lot worse.

[YVRGlen]

WABoating,

Thanks for your explanation. If I put a brand new potentiometer in, I imagine it comes with preset settings? Is the old one toast or can it be reset? Thanks in advance,

YVRGlen

[IDBoating]

There are no "settings" on a pot. Generally what happens is that the mounting system permits the body of the unit to rotate a bit, and you rotate the unit to set the output voltage to a certain value before tightening down its mounting screws (use Loctite). I don't know what the calibration procedure is for your unit, but since you're talking about a pot mounted on the throttle lever and NOT a pot mounted on the engine it's possible no calibration is required.

When pots are used as Throttle Position Sensors (TPS) on the actual throttle body of the engine itself, calibration is vital because that's one of the ways the ECU knows what the air input is doing. But on a throttle lever, you're just asking the engine to do something... a little slop in that is probably tolerated in the ECU firmware. The pot will be in the center of its rotation when clicked into neutral, so the ECU probably treats (as an example) the range 45-55% as "idle". Readings above or below that would ramp up the RPM's. So if the pot were "off" a few degrees it wouldn't matter, all you'd notice is that the RPM's would start ramping a bit earlier in forward or reverse.

As for the old unit, if it's truly bad then it's junk. Pots generally fail for one of two reasons: One of the element or wiper wears out due to the friction between them, or sufficient debris from that friction builds up internally and physically gets between the element and wiper. The measurable result is the same, intermittent output voltage, which is probably what you started noticing (because the ECU was noticing it!). Either way, there's no real repair possible. I looked up the spec sheet for this unit and it's a good device; sealed, with a conductive plastic element. For this application that's as good as they get. There's no way to "fix" it because you'd probably destroy the housing opening it up, and even then the element and/or wiper are probably shot and there's no repairing those.

Beyond a conductive plastic pot, a better and more reliable solution would be what is known as an absolute rotary encoder, particularly an optical device. These don't use a wiper rubbing against an element to create a voltage divider, but instead digitally track the rotation of the shaft and emit a voltage proportional to that rotation. Nothing rubs against anything (except normal shaft bushings, which will outlast your boat), all the important pieces have essentially infinite life, and if the unit is fully sealed they are impervious to contamination. However, they can be substantially more expensive.

Here's a rough diagram of one way to construct such a device:



My guess is that the throttle lever manufacturers have determined that the standard dual-pot versions are reliable enough, most of the time, to keep the price point reasonable.

Sorry for the long-winded answer. Like my son says, "It's Dad's area of expertise but I don't want to know that much about it."

[ericinmich]

.....

In an emergency situation (I'm thinking being stranded on the open ocean), it might be possible to use just one of the two pots to provide a common signal to the ECU. But that would take some careful experimentation by someone who understands what is going on electrically, and I'd only do it in dire circumstances and only just long enough to get to safety.

...

My knowledge is of automotive throttle position sensors (TPS) and there are two types. One uses reverse slope sensors (one goes 0.5-4.5 and the other the opposite as position increases.) The other uses a half slope and full slope sensor (one goes 0.5-2.5v and other 0.5-4.5v). The reason for this as a single point failure (sense wires shorting together) could give a false reading and provide an unsafe situation. The DFMEA on safety critical systems are done to eliminate single point failures.

It's likely that boats use similar TP Sensors.

[IDBoating]

That approach would add protection from shorts, true, but the sensors I've seen in marine applications haven't been like that - at least so far. The spec sheet for the sensor these guys are replacing, for example, includes the standard graph for resistance vs. rotation and the two elements are simply duplicates of each other - which means it would be possible to use one element to provide both signals in an emergency situation as I described above.

Side note: The spec sheet also provides two ordering options, for slotted and round mounting holes, the former allowing the "calibration by rotating the device" that I described.

[ericinmich]

Thanks for the link WAB. After thinking more about my reply, the more robust sensors that we use on cars/trucks came in to play about 15 yrs ago when we started going to electronic control. It looks like the boating industry is back where the cars were from the 70s to the ETC days (1995-2000 for most vehicles).

[IDBoating]

I can easily believe that! And thinking about the single point of failure... having two pots could, if configured properly, provide protection against a single point of failure. Either pot or its associated wiring could fail and the ECU would still have input as to the throttle's position. So it comes down to the question of whether you want the safety of a dual-confirmation system, or protection against a single point of failure by letting a single pot be enough input to run the engine. If I were designing the ECU I'd be tempted to prompt the user in the event of a single pot failure, telling them that they have (say) four hours of somewhat-less-safe operation before they're forced into limp mode. Thus they'd have time to get back to dock/ramp, but still be compelled to get it fixed.

[ericinmich]

If you design the system to use one reading because the other is failed it often is impossible to decide which one to believe. I would have to do a DFMEA on two equal slope design and those typically are xx page excel spread sheets where each possible type of failure mode is identified including it's likelihood.

The DFMEA puts more weight on designing out the most common types of failures in the full system and the most common is wire to wire short in the connection system (wire/pin/connector). With two equal slope signals, a failure in the wiring could become a latent failure (not detectable by the ECU) and the user keeps going without knowing the system is compromised. Then, a failure of the sensor could provide a no-detectable unsafe condition. Again, I'm speaking mostly of ETC systems. If the TPS is just providing the position of the blade, most of the time the engine would just run poorly or not at all. One really needs to have unequal signals for a robust system.

I'm sure we are boring most everyone else with this discussion!

[IDBoating]

If you design the system to use one reading because the other is failed it often is impossible to decide which one to believe.

Agreed. When I said it could provide protection against a single point of failure, I didn't mean to imply it would cover ALL failure modes. But some common ones, such as loss of signal from one pot or intermittent/erratic data from one, could be accommodated.

If the TPS is just providing the position of the blade...

Again, I'm speaking here of the throttle lever - the user's input device - and not the actual TPS on the engine itself.

BTW, it would also be possible to achieve your opposing-slope sensor behavior by reversing the connections to one of the two elements. I have examined the CAN reporting of the two element values and they do track, but I haven't looked at the voltages coming off the dual pots so I don't know if the MEFI ECU is translating one of them.

Yes, I'm sure everyone else's eyes glazed over long ago!