Battery not charging: Temporarily fixed it by disconnecting and connecting PCM connector

[Ericksonsf]

Hi all, I have a 2002 wrangler. I’ll start off by saying it has a new battery and new ish alternator, I don’t know exactly when the PO put it in but it has a date code for 2013. For the first 1000 of ownership it was great. Then driving home one day the battery stopped charging and the gauge was pointing to the left white dot. At home I checked grounds to see if that was the issue. From what I could tell, everything was grounded correctly. During this time, I unplugged the connector on the alternator going to the PCM. Plugging in this connector makes the battery charge as usual. GREAT! Or so I thought. This lasted about 20 miles before the problem persists again. I have gone through about 6 cycles of unplugging and plugging in this wire and it’s the same result everytime. I have tried cleaning the connections with a toothbrush but I could try harder. Is this caused by a bad connection or something else? Thanks.

 

[Chris]

Hi all, I have a 2002 wrangler. I’ll start off by saying it has a new battery and new ish alternator, I don’t know exactly when the PO put it in but it has a date code for 2013. For the first 1000 of ownership it was great. Then driving home one day the battery stopped charging and the gauge was pointing to the left white dot. At home I checked grounds to see if that was the issue. From what I could tell, everything was grounded correctly. During this time, I unplugged the connector on the alternator going to the PCM. Plugging in this connector makes the battery charge as usual. GREAT! Or so I thought. This lasted about 20 miles before the problem persists again. I have gone through about 6 cycles of unplugging and plugging in this wire and it’s the same result everytime. I have tried cleaning the connections with a toothbrush but I could try harder. Is this caused by a bad connection or something else? Thanks.

Since you’re getting a temporary fix by unplugging and reconnecting the PCM connector, it could indicate a few things. Here are some steps you might consider:

• Double-check for corrosion on the connectors and the pins, both on the alternator and the PCM side. Sometimes, a little corrosion can interfere with the connection, causing intermittent issues.
• Inspect the wiring for any signs of wear or fraying, particularly around the connectors. Any breaks or shorts in the wiring could lead to the charging issue.
• Although you mentioned checking the grounds, make sure all ground points related to the PCM and alternator are clean and secure. A weak ground can cause numerous electrical issues.
• If the harness and connections look good, it could be worth looking into whether the PCM itself could be the issue. Sometimes, they can fail over time. I would strongly suggest sending the PCM to @Wranglerfix (wranglerfix.com) to have it tested and ruled out.
• If you have access to a multimeter, measuring the voltage at the battery while running could give you more insight into what's happening. Ideally, you should see an increase when the engine is running.

Hopefully, one of these suggestions can help you narrow down the issue. Keep us posted on what you find! Good luck!

 

[Ericksonsf]

Since you’re getting a temporary fix by unplugging and reconnecting the PCM connector, it could indicate a few things. Here are some steps you might consider:

• Double-check for corrosion on the connectors and the pins, both on the alternator and the PCM side. Sometimes, a little corrosion can interfere with the connection, causing intermittent issues.
• Inspect the wiring for any signs of wear or fraying, particularly around the connectors. Any breaks or shorts in the wiring could lead to the charging issue.
• Although you mentioned checking the grounds, make sure all ground points related to the PCM and alternator are clean and secure. A weak ground can cause numerous electrical issues.
• If the harness and connections look good, it could be worth looking into whether the PCM itself could be the issue. Sometimes, they can fail over time. I would strongly suggest sending the PCM to @Wranglerfix (wranglerfix.com) to have it tested and ruled out.
• If you have access to a multimeter, measuring the voltage at the battery while running could give you more insight into what's happening. Ideally, you should see an increase when the engine is running.

Hopefully, one of these suggestions can help you narrow down the issue. Keep us posted on what you find! Good luck!

Thanks, I should also say when the battery stops charging it will not return to normal charging voltage unless the alternator PCM connector is unplugged and plugged back in. I feel like if it was a dirty connection it would work sometimes, stop working, then work again without me doing anything, is this true?

 

[Chris]

Thanks, I should also say when the battery stops charging it will not return to normal charging voltage unless the alternator PCM connector is unplugged and plugged back in. I feel like if it was a dirty connection it would work sometimes, stop working, then work again without me doing anything, is this true?

You're right about how a dirty connection typically behaves. Intermittent issues can point to a bad or corroded connection, which might work sometimes and not others. However, your situation seems more consistent since it only starts charging again after you cycle the PCM connector.

Given that it requires manual re-connection to get the battery charging again, it seems to suggest that there may be an internal issue with the PCM itself.

Here are a few more points to consider:

• Ensure that the PCM connector itself is making a solid connection. Sometimes, the clips or pins can loosen over time, leading to a poor connection that needs to be reset.
• Since it's consistently requiring a reset, it might be worth investigating whether the PCM is sending the correct signals to the alternator. If it’s not functioning properly, it may not engage the charging circuit reliably.
• You might want to have the alternator tested as well to confirm it's not having intermittent output issues. Sometimes, a failing voltage regulator inside the alternator can create similar symptoms.
• If you have access to a scan tool, you could check for any error codes in the PCM that might indicate other underlying issues.
• If you’ve checked all the connections and wiring thoroughly, and nothing seems to solve the issue, it may be worth replacing the PCM as a last resort, especially if testing shows it to be faulty. If the PCM ends up being the culprit, you'll find that wrangletrfix.com is your best place for a replacement PCM.

Keep us updated on what you find!