Check Engine Light On

[Esco]

The check engine light came on while out on the lake last weekend. I just got it back from the shop where the mechanic said that no error codes were showing when he read the computer. The boat runs fine, engine temp is fine, oil fine, etc. He said that nothing appears to be wrong. Rather than have him trace the wires or go any further, I figured I would trace the wires and check the connections myself to see if there are any problems. Anyone have a place to start other than just checking the wires and connectors? I can't just let the light stay on or it will drive me crazy. I also don't want to just disconnect the light in case any other problems pop up in the future.

The boat is a 1998 Sunsetter VLX with the 320 monsoon with EFI.

Thanks!

[MoonDawg]

You really need a copy of the GM MEFI-3 Trouble shooting and Repair Manual ($20).

To clear the MIL you need a Code Mate. Rinda sells one for half the skidim price.

I am not sure why you would have a MIL light and no code. I'll look through my manual and see what I come up with....

Edited September 8, 2006 by MoonDawg

[Pistol Pete]

Esco,

I have that book if you want it, I'll sell it for $10 + shipping.

Dawg,

What's the URL of that Rinda company?

[MoonDawg]

....

Dawg,

What's the URL of that Rinda company?

www.rinda.com

[Esco]

Pete,

I'll buy the book from you. Let me know how you want payment and we can arrange shipping.

[electricjohn]

If you have no codes, the lamp test circuit may be the culprit.

[MoonDawg]

According to the book you should never have a MIL light unless the onboard diagnostics generates a Diagnostic Trouble Code. (I wonder if the manual writer ever talked to the Software Engineer).

There is a case where if the condition goes away after 50 starts then the trouble code is erased. But the MIL light would also go away

There is also a case where the MIL light can be latched and will not go away until you reset the ECU with the CodeMate:

Latched diagnostics are:

DTC33 Map Sensor High Signal Voltage

DTC34 Map Sensor Low Signal Voltage

DTC41 Ignition Control Open Circuit

DTC42 Ignition Control Grounded Circuit

DTC44 Knock Sensor System Inactive

DTC51 Calibration Checksum Fail

There is one case where there are logged warning codes that are not blinked out so if your repair guy only had a CodeMate he would not have seen the codes. These warnings are:

Engine Overheat

Low Oil Pressure

Low System Voltage

Low Oil Level

General Warning 1

General Warning 2

Low Fuel Pressure

So my guess is you probably have an intermittent connection on a sensor that generates a latched code:

Check your MAP Sensor and Knock Sensor (for corrosion on connectors, bare wires etc.)

Check your MIL circuit (you need the CodeMate for this)

[MoonDawg]

You can clear the MIL light without the CodeMate by doing the following

Turn the key on engine off

Remove the cap on the DLC Connector

Put a paperclip between Pins A&B of the DLC Connector- (This puts the ECU in test mode).

Move the throttle from neutral to full throttle and back to neutral.

Remove the paperclip from DLC connector

Turn the key off and wait for 20 seconds

Reconnect the cap on the DLC connector.

Tun the key on, engine off - The MIL lamp should be off

[D-GOOSE]

Your gas cap is not on tight. Check to make sure you have it one.

[Pistol Pete]

Uhhh yeah,

And maybe your seat belt is unbuckled.