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Crazy issues...

vglnte1

By vglnte1
in 996 TT, 996 TT S, 996 GT2

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vglnte1 Member

vglnte1

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So, car has never skipped a beat. Removed the cardan shaft only to go dyno. Drove fine for 30min. Then every light possible came on. First was battery discharge light, then brake distribution, then all the abs, psm. Car went in limp mode. Brought it home and read the codes. Was just o2 sensors and cats. Erased everything. Went to start the car again and it won't start, just cranks and smells very strong of gas. Just tried to read codes again, none found.

Hooked the shaft back up. Car started and idled fine. Drove it 30 feet and brake distribution came back on. Voltage metered pegged. Battery seems hot to the touch. Soon as I slow down all the lights go back off. Car won't make any boost.

Lost......

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JFP in PA Member

JFP in PA

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So, car has never skipped a beat. Removed the cardan shaft only to go dyno. Drove fine for 30min. Then every light possible came on. First was battery discharge light, then brake distribution, then all the abs, psm. Car went in limp mode. Brought it home and read the codes. Was just o2 sensors and cats. Erased everything. Went to start the car again and it won't start, just cranks and smells very strong of gas. Just tried to read codes again, none found.

Hooked the shaft back up. Car started and idled fine. Drove it 30 feet and brake distribution came back on. Voltage metered pegged. Battery seems hot to the touch. Soon as I slow down all the lights go back off. Car won't make any boost.

Lost......

 

Batteries should get warm, but not hot, which is usually a sign of trouble.  I would load test the battery and the charging system as spurious MIL lights are often voltage related.

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vglnte1 Member

vglnte1

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So, car has never skipped a beat. Removed the cardan shaft only to go dyno. Drove fine for 30min. Then every light possible came on. First was battery discharge light, then brake distribution, then all the abs, psm. Car went in limp mode. Brought it home and read the codes. Was just o2 sensors and cats. Erased everything. Went to start the car again and it won't start, just cranks and smells very strong of gas. Just tried to read codes again, none found.

Hooked the shaft back up. Car started and idled fine. Drove it 30 feet and brake distribution came back on. Voltage metered pegged. Battery seems hot to the touch. Soon as I slow down all the lights go back off. Car won't make any boost.

Lost......

 

Batteries should get warm, but not hot, which is usually a sign of trouble.  I would load test the battery and the charging system as spurious MIL lights are often voltage related.

What's the best way to do that

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JFP in PA Member

JFP in PA

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So, car has never skipped a beat. Removed the cardan shaft only to go dyno. Drove fine for 30min. Then every light possible came on. First was battery discharge light, then brake distribution, then all the abs, psm. Car went in limp mode. Brought it home and read the codes. Was just o2 sensors and cats. Erased everything. Went to start the car again and it won't start, just cranks and smells very strong of gas. Just tried to read codes again, none found.

Hooked the shaft back up. Car started and idled fine. Drove it 30 feet and brake distribution came back on. Voltage metered pegged. Battery seems hot to the touch. Soon as I slow down all the lights go back off. Car won't make any boost.

Lost......

 

Batteries should get warm, but not hot, which is usually a sign of trouble.  I would load test the battery and the charging system as spurious MIL lights are often voltage related.

What's the best way to do that

 

 

You need a system load tester to do this:

 

OTC3182.jpg

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JFP in PA Member

JFP in PA

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Can I just take the alternator to a auto zone? Same thing?

 

No. a load test for the alternator is a dynamic process; with the car running, the system ramps up an electrical load on the system as shows how it responds.  AutoZone testing is more for "it works or it doesn't work", like a light bulb.

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JFP in PA Member

JFP in PA

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Could a bad voltage regulator cause the car to go into limp mode and make no boost?

 

Yes, it is possible.  Because of all of the electronics on these cars, spurious voltage excursions can lead to all sorts of weird issues.  The DME can basically "loose its mind" when it does not have the operating voltage it expects, as can many of the various sensors on the engine.

 

You can test the alternator output with something as simple as a digital multimeter.  At idle, the system should be around 14V or so.  A load test on the alternator would monitor the voltage output as the electrical load on the system increases, which would give you additional data, but a simple output voltage would be a good starting point.

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