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ECM Code 15

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Old Apr 25, 2017 | 10:37 AM
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Default ECM Code 15

My 85 just started showing code 15 and at the same time the main cooling fan starts. This happens when the engine is cold. Are the 2 related?
​​​​​​​Thanks
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Old Apr 25, 2017 | 10:52 AM
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I think so
iirc 15 is a coolant temp sensor error
so the fans are turned on to protect the engine
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Old Apr 25, 2017 | 11:31 AM
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Originally Posted by belairbrian
I think so
iirc 15 is a coolant temp sensor error
so the fans are turned on to protect the engine
​​​​​​​Bad sensor then ?
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Old Apr 25, 2017 | 08:55 PM
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OK I found a flow chart for code 15 and I'm stuck at the part probe yellow wire with a voltmeter and I got .5 volts which is OK. It says Sensor ground circuit open, faulty ecm conn or ecm. How should I proceed? Electrical is above my skill level. .
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Old Apr 25, 2017 | 09:12 PM
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Originally Posted by spro2395
OK I found a flow chart for code 15 and I'm stuck at the part probe yellow wire with a voltmeter and I got .5 volts which is OK. It says Sensor ground circuit open, faulty ecm conn or ecm. How should I proceed? Electrical is above my skill level. .
I don't believe I've ever seen anything in CODE 15 diagnostics that mentions .5V as being a "good/expected" value.

Have you actually checked the CTS resistance values for the engine when at running temperature.

I'm assuming you're at FIG 32 of the FSM. Is that correct? Check the resistance of the CTS using the chart in FIG 32

If the engine is COLD check it cold then maybe start and run to something near the expected run temperature and check.

Last edited by WVZR-1; Apr 25, 2017 at 09:24 PM.
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Old Apr 26, 2017 | 07:17 AM
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Originally Posted by WVZR-1
I don't believe I've ever seen anything in CODE 15 diagnostics that mentions .5V as being a "good/expected" value.

Have you actually checked the CTS resistance values for the engine when at running temperature.

I'm assuming you're at FIG 32 of the FSM. Is that correct? Check the resistance of the CTS using the chart in FIG 32

If the engine is COLD check it cold then maybe start and run to something near the expected run temperature and check.
Yeah. Bad eyes, I thought it read .5 when really it's 4-6 volts so the reading I got of .5 is low. Yes I'm looking at Fig 32 in my FSM
​​​​​​​So I feel like this might be over my ability but hopefully not!
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