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Temp Sensor fault...


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JamesCole
Posted (edited)

Hello guys, 

 

Great community here and happy to be part of...

2008 Malibu Response LXi 

Looking to source a part number to replace this part, I get an engine fault on the screen every time  I use the boat...

Cat_B_Tempsensor SPN 65672 CM 0 Voltage short or above normal RNG FMI 3 OC 2

Thanks

JC

 

 

 

Edited by JamesCole
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Posted (edited)

I would not recommend replacing a failed post catalyst temperature sensor.  They tend to fail often due to the sensor element being damaged when exposed to heat and moisture in the exhaust downpipe.  Even the newer replacement sensors are prone to failure, just not as often as the original sensors were.  The MEFI5B ECM used in 2008 Indmar engines were designed to use the post catalyst temperature sensors as a very basic way to check for catalyst efficiency by testing the exhaust heat.  Indmar catalyst engines in 2007 had no post cat sensors, and the 2009 or newer catalyst engines used post cat O2 sensors (and a different ECM).

Indmar MEFI5B ECMs can be reprogrammed by any Indmar dealer that has Diacom and the authoring files provided by Rinda to Indmar dealers.  The new calibration will prevent a fault alarm at the helm or an engine derate when the code occurs.  The fault codes will still be active in the ECM, but they will not cause an alarm or any running issues after reprogramming. 

The alternate repair is to rewire the existing post catalyst temperature sensor harnesses.  The harness wires on the sensor can be cut between the metal sensor and the connector that plugs into the engine harness.  Just wire in a 470 ohm resistor between the two cut harness wires, tape it up or cover it with heat shrink, and then reconnect the modified sensor wire to the engine harness connector just like it was before.  This will send a signal to the ECM which mimicks a properly working post cat temperature sensor to prevent alarms or running issues. 

There are service bulletins from Indmar for both of these repair methods.

Edited by csleaver
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JamesCole

Thanks so much @csleaver, great info...

 

For the 470 ohm resistor, which amperage works? 

 

As for wiring the o2 sensors have 4 wires in them 2 black 1 blue and 1 white... am I looking at the right sensor?

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5 minutes ago, JamesCole said:

For the 470 ohm resistor, which amperage works? 

12v/470 Ohms = 0.025 Amps. 

0.025A^2*470Ohms = 0.31 Watt, so go with a 1/2 Watt resistor.

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JamesCole

Thanks Gary... 

 

You guys happen to know which of the wires have to be soldered trough the transistor?

 

I have 2 black, 1 blue, 1 white. 


Thanks

JC

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The pre-catalyst O2 sensors have 4 wires and are located on the ETX exhaust manifold (don't mess with those wires), but the post catalyst temperature sensors have 2 wires and are located on the stainless down pipe between the exhaust manifold and the rubber exhaust hose.

Here are some links with instructions to wire a 470 ohm resistor in place of the post catalyst exhaust temperature sensor at the stainless down pipe:

https://www.dropbox.com/scl/fi/s8h7ijg9zixjcrc5tvh31/post-cat-temp-470-ohm-resistor-install.pdf?rlkey=wnymhd4s269o0tseuw3on7ovr&dl=0

https://www.dropbox.com/scl/fi/alg8p1hcj40b0bxs7p8em/Post-Cat-Resistor-Install.pdf?rlkey=3q5vy3i5v1nxxltzwepsoudxx&dl=0

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Beautiful! 

 

Thanks for the info guys! Worked great...

 

Boat accelerates a little better and feels stronger, not sure that makes sense since rear O2s are only to monitor cat efficiency...

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