Confirmation of bad PCM

SHVLHEAD68

MEMBER
1994 SUZUKI SIDEKICK
4 CYL
4WD
AUTOMATIC
137,000 MILES

Confirmation of bad PCM. The alternator only charges at an idle (it's been checked and is good), when the battery gets low the battery light on the dash doesn't come on, the check engine light comes on every 100 miles or so, when jumping the terminal to get the cel to flash the code it doesn't flash at all. When the car is at an idle, the battery charges slowly, starting at like 11.4 volts and if you let the car idle long enough (about 10 min) the voltage works its way up to 14.2. With all these symptoms, is the probable cause a bad PCM (power control module)

7 Replies

SATURNTECH9

MECHANIC
30,869 POSTS

I just looked at the wire diagram for your alternator and it doesn't show the pcm in the diagram having anything to do with the alternator. Key on engine off test the white with a green tracer wire it should have battery voltage to it. Also key on engine off check the black wire with a white tracer it should have battery voltage too.

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Thursday, December 30th, 2010 AT 1:53 AM

MERLIN2021

MECHANIC
17,250 POSTS

Why would you think the PCM is bad? I read that the voltage is regulated by a voltage regulator, not the PCM. Check wiring harness and voltage regulator. Test this way.
ON-VEHICLE TESTING

ALTERNATOR PERFORMANCE TESTING

1. If battery is overcharged go to BENCH TESTING. If battery is undercharged, check
alternator wiring harness connections and drive belt tension. Ensure battery is fully charged.
Connect a voltmeter to alternator "B" terminal and ground. Connect ammeter positive lead to
alternator "B" terminal. Connect ammeter negative lead to positive side of battery and start
engine.
2. With all accessories off, increase engine speed from idle to 2000 RPM and read meters.
Voltmeter reading should be 14.4-15.0 volts at 68°F (20°C). Voltage reading will vary
depending on regulator case temperature. Ammeter should read about 10 amps. Turn engine
off.
3. If voltage is higher than standard value, check brush ground. See BENCH TESTING. If
brush ground is okay, replace IC regulator.
4. Load test with engine running at 2000 RPM and headlights and heater blower motor on. If
current is less than 20 amps, go to BENCH TESTING.
CAUTION: DO NOT confuse polarities of IG terminal and "L" terminal. DO
NOT create a short circuit between IG terminal and "L" terminal.
Always connect these terminals through a test light. DO NOT
connect a load between "L" and "E" terminals.

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Thursday, December 30th, 2010 AT 1:57 AM

MERLIN2021

MECHANIC
17,250 POSTS

As you can see the regulator is built into the alternator, inspect wires and replace alt if OK.

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Thursday, December 30th, 2010 AT 2:01 AM

SHVLHEAD68

MEMBER
10 POSTS

Please read question and all answers.I checked the wires on the plug to the alternator and I get battery voltage to both. All wires are good and alternator is good. Could it be that the starter is draining the system, since the PCM isn't in question?

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Friday, December 31st, 2010 AT 11:38 PM

MERLIN2021

MECHANIC
17,250 POSTS

So the MIL does not come on with key on engine off? If you post your email, I will send the info you need to repiar the circuits, it's 36 pages with diagrams, so too much to post here.
Drop an email to
merlin2021@comcast. Net put suzuki in the subject and I'll send you a copy.