QuestionI was told that problems with my 1999 Pontiac Montana that stranded us by the road were because of the alternator (1 year old). It took four roadside jump starts to go 15 miles to get it home, one was an overnight full charge - lasted 5 miles. I replaced the alternator, same issues - battery light comes on, starts blinking, engine shuts off. I replaced the battery (also 1 yr old). Did not correct anything. The vehicle will die as soon as the new battery runs down, the lights blink and I pull off the road. If it doesn't simply die, putting it into park will finish it off. I cannot take a chance driving the 30 miles to a dealer (isolated in Pocono mountains.) I got a factory manual but have no diagnostic tools.
Now what? BCM?
AnswerHi david:
This is right out of our service manual it's a 5 column chart and it doesn't cut and paste right sorry. what it's looking for is if the engine control module is sending the correct "turn on siganl" to the alternator and to make sure the power feed back to the batery is good a corroded fuseable line or broken link could do this as well. It may not be a ECM issue but the chart will guide you though it. hope it helps and you can figure out waht it's saying.
Battery Is Undercharged or Overcharged
Step
Action
Value(s)
Yes
No
1
Inspect the ignition (IGN) 1 fuse.
Is the ignition (IGN) 1 fuse open?
—
Go to Step 2
Go to Step 3
2
Repair the short to ground in CKT 39.
Is the repair complete?
—
Go to Charging System Check
—
3
1. Disconnect the generator connector.
2. Turn the ignition switch to the RUN position.
3. Attach a scan tool to the data link connector (DLC).
4. Clear any diagnostic trouble codes (DTCs).
5. Select MISC TESTS, ENG OUTPUTS, and GEN L TERM.
6. Command the generator ON.
7. Measure the voltage from the generator connector terminal B to ground.
Is the voltage equal to the specified value?
5V
Go to Step 4
Go to Step 9
4
Measure the voltage from the generator battery (Bat) terminal to ground.
Is the voltage equal to the specified value?
9-14V
Go to Step 5
Go to Step 12
5
1. Reconnect the generator connector.
2. Ensure that all of the accessories are OFF.
3. Run the engine at a fast idle.
4. Measure the voltage across the battery.
Is the voltage equal to the specified value?
13-16V
Go to Step 6
Go to Step 8
6
Load test the generator. Generator Assembly Check
Did the generator test OK?
—
Go to Step 7
Go to Step 8
7
Replace the battery. Refer to Battery Replacement.
Is the repair complete?
—
Go to Charging System Check
—
8
1. Check for poor connections at the generator.
2. If connections are ok, replace the generator. Refer to Generator Replacement .
Is the repair complete?
—
Go to Charging System Check
—
9
Inspect for a poor connection or an open in CKT 225.
Is there a poor connection or an open in CKT 225?
—
Go to Step 10
Go to Step 11
10
Repair the poor connection or the open in CKT 225.
Is the repair complete?
—
Go to Charging System Check
—
11
Replace the powertrain control module (PCM). Powertrain Control Module Replacement/Programming
Is the repair complete?
—
Go to Charging System Check
—
12
Repair one of the following conditions:
• The open in CKT 2
• The fusible link to the generator battery (Bat) terminal
Is the repair complete?
—
Go to Charging System Check
—
