For a 1999 Corvette
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Battery Is Undercharged or Overcharged (Low/High Voltage Message)
Battery is Undercharged or Overcharged (DIC-Low or High Voltage warning message) Step
Action
Value(s)
Yes
No

DEFINITION: The LOW VOLTAGE or HIGH VOLTAGE message is displayed across the driver information center.

1
Were you sent here from the Charging System Check?
--
Go to Step 2
Go to Charging System Check

2
Recharge the battery if necessary. Refer to Battery Charging .
Load test the battery.
Does the battery pass the load test?
--
Go to Step 4
Go to Step 3

3
Replace the battery. Refer to Battery Replacement .

Is the repair complete?
--
Go to Charging System Check
--

4
Start the engine and allow it to idle in park.
Load the electrical system by turning on the highbeam headlamps and the heater blower to high.
Connect a DMM to the vehicle battery and measure the voltage.
Is the voltage within specified values?
13.5-15.0 V
Go to Charging System Check
Go to Step 5

5
Connect the red alligator clip of the J 41450-B CS Generator Electronic Tester to the generator output terminal.
Connect the black alligator clip to the generator housing.
The green POWER lamp of the tester should light and remain lighted while the tester is being used.
Does the green POWER lamp of the tester light?
--
Go to Step 6
Go to Step 7

6
With the alligator clips connected.
Disconnect the generator four way connector.
Locate the matching four way connector of the J 41450-B and connect it to the generator.
Does the red DIAGNOSTIC lamp of the tester light?
--
Go to Step 8
Go to Step 30

7
Repair the open in the generator output circuit or the battery ground circuit.

Is the repair complete?
--
Go to Charging System Check
--

8
Prior to connecting a carbon pile load tester, make sure that the load dial is completely turned to the off position.
Connect the leads of the carbon pile to the vehicle battery.
Connect an inductive ammeter to the generator output circuit.
Start the engine and allow it to idle.
Does the red DIAGNOSTIC lamp of the tester light?
--
Go to Step 30
Go to Step 9

9
Increase the engine speed to 2500 RPM.

Does the red DIAGNOSTIC lamp of the tester light?
--
Go to Step 30
Go to Step 10

10
Maintain the engine speed at 2500 RPM
Turn on the load of the carbon pile tester.
Using caution not to load the battery beyond manufacturers load test values, increase the load while monitoring generator output current.
As the load is increased, is the generator capable of producing the amount of load test current specified in generator usage?

Refer to Generator Usage .
--
Go to Step 11
Go to Step 12

11
With the engine speed at 2500 RPM and the generator operating at load test value, is the red DIAGNOSTIC lamp of the tester lighted?
--
Go to Step 30
Go to Step 12

12
Maintain the engine speed at 2500 RPM and continue to operate the generator at the load test value.
Using a DMM measure the voltage from the generator output terminal to the battery positive terminal.
Is the voltage under the specified value?
0.5 V
Go to Step 13
Go to Step 14

13
Maintain the engine speed at 2500 RPM and continue to operate the generator at the load test value.
Using a DMM measure the voltage from the generator housing to the battery negative terminal.
Is the voltage under the specified value?
0.5 V
Go to Step 16
Go to Step 15

14
Turn off the engine.
Disconnect the battery negative terminal.
Inspect the circuit between the battery positive terminal and the generator output terminal for high resistance.
Disassemble and clean or replace the terminals and wire in this circuit as necessary.
Is the repair complete?
--
Go to Charging System Check
--

15
Turn off the engine.
Inspect the circuit between the negative battery terminal and the generator housing for high resistance.
Disassemble and clean or replace the terminals and wire in this circuit as necessary.
Is the repair complete?
--
Go to Charging System Check
--

16
Turn the ignition switch to the off position.
Disconnect the negative battery terminal.
Disconnect the circuit 2 from the starter terminal.
Using a DMM measure the resistance of this circuit from the generator four wire connector terminal D to the starter connector terminal.
Is the resistance within specified values?
0-2 ohms
Go to Step 18
Go to Step 17

17
Repair the open in circuit 2 between the starter terminal and the generator connector.

Is the repair complete?
--
Go to Charging System Check
--

18
Disconnect the powertrain control module connector C2.
Connect a DMM between the powertrain control module connector C2 terminal 52 and the generator four wire connector terminal C.
Measure the resistance of circuit 23.
Is the resistance within specified values?
0-2 ohms
Go to Step 19
Go to Step 24

19
With the powertrain control module connector C2 and the generator four wire connector disconnected, measure the resistance to ground of circuit 23.

Is circuit 23 shorted to ground?
--
Go to Step 20
Go to Step 25

20
With the powertrain control module connector C2 and the generator four wire connector disconnected, measure circuit 23 for a short to voltage.

Is circuit 23 shorted to voltage?
--
Go to Step 26
Go to Step 21

21
Disconnect the powertrain control module connector C2.
Connect a DMM between the powertrain control module connector C2 terminal 15 and the generator four wire connector terminal B.
Measure the resistance of circuit 225.
Is the resistance within specified values?
--
Go to Step 22
Go to Step 27

22
With the powertrain control module connector C2 and the generator four wire connector disconnected, measure the resistance to ground of circuit 225.

Is circuit 225 shorted to ground?
--
Go to Step 23
Go to Step 28

23
With the powertrain control module connector C2 and the generator four wire connector disconnected, measure circuit 225 for a short to voltage.

Is circuit 225 shorted to voltage?
--
Go to Step 29
Go to Charging System Check

24
Repair the open in circuit 23.

Is the repair complete?
--
Go to Charging System Check
--

25
Repair the short to ground in circuit 23.

Is the repair complete?
--
Go to Charging System Check
--

26
Repair the short to voltage in circuit 23.

Is the repair complete?
--
Go to Charging System Check
--

27
Repair the open in circuit 225.

Is the repair complete?
--
Go to Charging System Check
--

28
Repair the short to ground in circuit 225.

Is the repair complete?
--
Go to Charging System Check
--

29
Repair the short to voltage in circuit 225.

Is the repair complete?
--
Go to Charging System Check
--

30
Disconnect the powertrain control module connector C2, and the generator four wire connector.
Turn the ignition switch to the on position.
Measure circuit 225 for a short to voltage.
Is circuit 225 shorted to voltage?
--
Go to Step 31
Go to Step 32

31
Repair the short to voltage in circuit 225.

Is the repair complete?
--
Go to Step 32
--

32
Replace or repair the generator. Refer to Generator Replacement .

Is the repair complete?


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Charging System Check
Charging Diagnostic System Check Step
Action
Normal Result(s)
Abnormal Result(s)*

1
Inspect the battery for proper installation.
Inspect the battery for cracking or other damage.
Inspect the battery terminals for proper connection.
Inspect the battery terminals for excessive corrosion.
Inspect the battery cables for proper installation.
Check that all ground connections are clean and tight.
Inspect the battery hydrometer (eye) for a green dot.
Connect a DMM between the battery's positive and negative terminals.
Ensure that any aftermarket accessory equipment is de-energized.
Observe the battery voltage.
• The battery is properly installed.

• The battery is free from physical damage.

• The battery terminals are free from corrosion.

• The battery cables are properly connected.

• The battery cables are properly installed.

• The battery hydrometer displays a green dot.

• Battery voltage is approximately between 11.5 to 13.0 volts.
• Battery Common Causes of Malfunction

• Battery does not meet minimum voltage requirement. Refer t Battery Charging

• Battery Not Operating Properly

2
Remove the DMM from the battery terminals.
Perform a load test on the battery. Refer to Battery Check
Battery maintains a specified voltage level according to the manufacturer's battery rating.
Battery does not maintain the specified voltage level during the load test. Replace the battery. Refer to Battery Replacement

3
Install the scan tool to the diagnostic link connector.
Turn the ignition switch to the ON position.
Select display DTC function with the scan tool.
Check for any stored PCM, BCM, or communication DTCs related to theft deterrent, starting or charging system operation.
No DTCs are stored in memory or current status.
• DTC is stored in memory or current status (refer to appropriate DTC table).

• Scan Tool Does Not Communicate with Components

4
Start the engine and allow it to idle in PARK.
Press the HVAC MODE control button until the LOWER floor position is displayed.
Depress the fan control button until the fan reaches high speed.
Turn the headlamp switch to the ON position (headlights ON).
Move the wiper switch to the HI position (maintain some moisture on the windshield while the wipers are in operation).
Maintain engine speed between 800 and 1000 RPMs.
Connect a DMM between the battery positive terminal and negative terminal.
Observe the voltage reading at the DMM.
• The generator operates without unusual noises.

• The Battery/CHECK GAGES indicators on the instrument cluster extinguish after the engine is started.

• The SERVICE ENGINE SOON malfunction indicator lamp extinguishes when the engine starts.

• The DMM reads approximately between 12.0 and 16.0 volts while the engine is idling.
• Battery Is Undercharged or Overcharged

• Charge Indicator Always On

• Volt Gage Inaccurate or Inoperative

 

Theres there entire troubleshooting procedure.

Make sure pin D is able to read battery voltage. Its as simple as disconnecting the connector on top of the alternator and reading pin D with a volt meter to ground. It should read exacty what batter voltage reads. (engine Off)


A fuseable link shouldnt have any resistance. What does your Ohm meter read when you short the probes together?

 

Thank you everyone for you help. Everything seems to be checking out ok but still getting P1637. I don't really know what to do with the full trouble shooting because I don't have all those special tools. Here are the results I got from your previous questions.

Pin D of the alternator to ground 12.69 V

Batt + to ground 12.77 V

0.5 ohms when probes are put together

13.87 across battery when loaded with heater and high beams (the red part of the procedure above)

 

P1637 is a PCM related code. Do this for me, with the ignition in the "on" position (engine off, not running)measure the voltage at the alternator connector pin B. This pin is next to the unused pin and is a small red wire. You should get 5 volts. If not you may need to check the PCM connector. Let me know what you get.

PS: Double check with the people that did your alternator bench testing to see if they can/did test the PCM interface circuits in the alternator. Red and gray wires as shown on Post 15. If you need to check the circuits to the PCM I can post a picture of the PCM connection.

 

Here is the PCM connector (RED) for you in case you need it. The Gray wire is Pin 52 and the Red wire is Pin 15.

 

Ok with the key in the on position and engine not running I disconnected the 4 wire connector and measured pin B to the alternator case ground and got 10.70 V. This seems like a problem since its supposed to be 5 V. If you could post that PCM related info and some instruction that would be great. I know nothing about the PCM so please keep it basic if you can (I'm not even sure where it's located). Edit: (I have since learned that it is located behind an access door once you get the right front tire off. It sounds like this one is going to be more of a pain to test.)

I also know the place where I bench tested my alternator cannot check for PCM connections.

Also I have some new codes I don't know if they are just from pulling the connector while in the on or not but here they are:
P1637
P1638
C1255
B2723
(I also accidentally started the car last night with the 4 wire alternator plug out so I don't know if any of those codes would be thrown from that)

Those are all history codes by the way.
As always thanks for your help its much appreciated!

 

PM or email me with your phone number so we can talk. It is much better than trying to type out info. I can get you the FSM info so you can read and better understand my input. We can solve this Grasshopper. Mr. Sam, at your service.

Just kidding about the Grasshopper comment, do you know where that quote comes from?

 

hey everyone just an update from my hopeful solution I discovered today. When I got home I started receiving a charging system fault so I pulled out my DMM and found no continuity between the alternator B+ and battery positive. I investigated this more and had to drop the exhaust and pull the starter. What I found was the wire from the alternator to the starter is stranded wire and it had broken free from the ring lug that connects to one of the studs on the starter. I replaced it with a new ring lug and my car is fixed! Or atleast I havent got any codes in the past 4 hours so far. Im doing a 100 mile drive tomorrow so hopefully all goes well. Thanks Dadaroo and Bill and everyone for their input!

 

That is good news. That is one thing about using an ohmmeter to check out a circuit that can carry a lot of current. A "good" resistance reading can be misleading sometimes. Even one strand could have given an "ok" reading.

I am sure you will let us know if anything else crops up.