Sensor Error Codes - need help

[prostar205]

Just got my boat's ECM read from a dealer (not a MC dealer - they are too busy and not accepting customers that did not buy their boat from them). Came back with 3 errors codes 1) MAP Sensor Voltage Low (code 34), 2) Crank Signal Fault (code 81) and 3) Cam Signal Fault (code 81). Dealer thinks it may be a bad ground causing all 3 errors. I replaced the MAP Sensor about 18 months ago.

Attached is the wiring diagram for my engine (8.1L).

Any help or suggestions before I replace these sensors? I really don't want to replace parts until I find the issue that is causing this to happen.

Thanks in advance for the help.

[93Prostar190]

I agree on bad engine ground, or weak battery ….

[prostar205]

I agree on bad engine ground, or weak battery ….

Batteries are new (Group 31 Odysseys). I think it's a bad ground somewhere just don't know how to find it.

[prostar205]

Can someone post of picture of where the cam position sensor is located on a 2002 8.1L engine?

Also, does anyone have the wiring diagram for the MEFI3 for a 2002 8.1L engine?

Thanks.

[robadele]

Batteries are new (Group 31 Odysseys). I think it's a bad ground somewhere just don't know how to find it.

Easiest option may be to run a temporary new ground between the battery, the motor, and possibly the ECM. If the problem goes away, you can then spend more time finding and cleaning the grounds.

[ahhudgins]

If checking all of your grounds reveals nothing, you may want to remove the plugs on the ECM and check the pins for any corrosion, which is rare. Disconnect your battery first. Your crank and cam sensors both share +V on J2 pin 17, and ground on J2 pin 18. The +V for those sensors comes in on J2 pin #1, which is why I suggest checking the connectors. The MAP sensor shares a ground (J2 pin 3) with the oil and ECT sensors but you didn't mention errors with those two sensors. The ground for the ECM comes from several pins of J1 (smoke colored connector).

[prostar205]

If checking all of your grounds reveals nothing, you may want to remove the plugs on the ECM and check the pins for any corrosion, which is rare. Disconnect your battery first. Your crank and cam sensors both share +V on J2 pin 17, and ground on J2 pin 18. The +V for those sensors comes in on J2 pin #1, which is why I suggest checking the connectors. The MAP sensor shares a ground (J2 pin 3) with the oil and ECT sensors but you didn't mention errors with those two sensors. The ground for the ECM comes from several pins of J1 (smoke colored connector).

Thanks for confirming this. That was my understand also.

On the attached MEFI4 wiring diagram in my original post, it shows a ETC (Electronic Throttle Control) and TAC plugs. Indmar (Larry Engelbert) told me that my 2002 does not have those two plugs. I believe those are for the DBW (Drive By Wire) feature that did not come along until 2005. The rest of the wiring diagram should be accurate. Larry also told me my boat would of had a MEFI3 but they never put MEFI3s in boats with the 8.1L engine - only MEFI4s.

Question - looking at the wiring diagram, can someone tell me what direction the ECM connectors (smoke and clear) are facing in the diagram? Are those looking at the connector with the wiring attached or looking at the ECM?

[lakedrum03]

Question - looking at the wiring diagram, can someone tell me what direction the ECM connectors (smoke and clear) are facing in the diagram? Are those looking at the connector with the wiring attached or looking at the ECM?

That answer is relative. It depends on how they mounted the bulkhead connectors. I verify orientation by wire color and then mark a couple pins so I know for later.

[prostar205]

What are people's thoughts on continued use of my boat with the codes it's throwing? I want to get out on it one more time this upcoming weekend.

I plan on trying to find a ground problem that may be a causing the low voltage error code to the MAP sensor and also see if there is a ground issue with the Cam and Crank Position sensors. However, the Cam and Crank sensor are original (2002) parts. Is it weird that both would go out at the same time? Coincidence or issue with the wiring?

Thoughts??

[skydyvyr]

Dude, sorry to thread jack, but Union Marine is turning away service on boats they didn’t sell?!? That is insane.

Granted, they only became a dealer like five years ago (I think) so maybe not so much knowledge around boats of your era.

—Sky

[prostar205]

Dude, sorry to thread jack, but Union Marine is turning away service on boats they didn’t sell?!? That is insane.

Granted, they only became a dealer like five years ago (I think) so maybe not so much knowledge around boats of your era.

—Sky

Correct, they told me in July that unless I purchased my boat from them, they would not service it. I've had my boat for almost 19 years. As you point out, they've only been a MC dealer for 4-5 years now. When there were two MC dealers (Union and Northwest MasterCraft in Redmond), Union would not work on Indmar engines. Their tech's were not certified on Indmar engines. Since Northwest MasterCraft shut down last year, a couple of their techs went over to Union. They are now working on Indmar boats but only if you purchased your boat from them.

Oh well, there are other dealers that can work on them. I ended up going to Seattle Watersports in Kenmore. Great guys and knowledgable.

[curver900]

What are people's thoughts on continued use of my boat with the codes it's throwing? I want to get out on it one more time this upcoming weekend.

I plan on trying to find a ground problem that may be a causing the low voltage error code to the MAP sensor and also see if there is a ground issue with the Cam and Crank Position sensors. However, the Cam and Crank sensor are original (2002) parts. Is it weird that both would go out at the same time? Coincidence or issue with the wiring?

Thoughts??

The odds of both failing at the same time are 0.001%.. give or take. That information alone would lead me to the ground.. but and a big but if those are original battery cables that have laid in the hull for 20 years IMHO I would replace all of them. Take out your trusty voltmeter and see what the resistance is across them...

good time to upgrade too larger cabling while doing it.. I replaced all of mine 3 years ago or so... some of those cables were not in the best conductive condition...

good luck with a solution

I just went to the local fleet farm store and bought bulk 2ga and ends and soldered them on making custom cables.. pretty easy.. need a torch to heat the cable enough to accept the solder

[prostar205]

The odds of both failing at the same time are 0.001%.. give or take. That information alone would lead me to the ground.. but and a big but if those are original battery cables that have laid in the hull for 20 years IMHO I would replace all of them. Take out your trusty voltmeter and see what the resistance is across them...

good time to upgrade too larger cabling while doing it.. I replaced all of mine 3 years ago or so... some of those cables were not in the best conductive condition...

good luck with a solution

During the winter of 2020/2021 all batteries where changed to 2 Odyssey Group 31s along with a ProMariner 20A charger and all new battery cables (2 AWG) all around. Only original battery cables are the Power and Ground cables going from the batteries to the helm. All grounds and positive wires in the engine compartment were changed.

[prostar205]

I spoke to Allen at Technical Services Inc. (Thank You again Waterlogged882). There are 3 ground wires on the J1 connector (smoke colored backshell) on the ECM (MEFI4) on the 8.1L engine. All 3 terminate on a single ring terminal on the engine block. There is a 4th ground wire that comes off the ALDL (Assembly Line Data Link) connector. This is the connector back by the ECM that the dealer uses to run your diagnostic codes. Does anyone know where that ring connector is located with the ground wires? If not, I will be tracing the grounds from the J1 and ALDL connectors to see if that is my ground problem. Any help and preferably pictures would be GREAT!!!

[sand2snow22]

Shouldn't they be on the block? Call Indmar, press 2 for GM service and speak with JT. He will help. Also, Bakes knows there stuff in your neck of the woods if you can get in.