2011 Dodge Grand Caravan 3.6l alternator not charging

Hello, I have a 2011 Dodge Grand Caravan 3.6l and the alternator is not charging. I changed the alternator out and it is still not charging. So I check the gen sense and field control wire for voltage and I am not getting any voltage at the connector going to the alternator.I found on the mopar website that pin 24 on the BLACK MODULE-POWERTRAIN CONTROL C1 is where the gen sense wire goes to I unhooked the connector from the PCM and I get 5 volts at the PCM pin 24. So I figured there was a short in the wire. I cut the wire about half way to the alternator and check for voltage. With the key off I get 10.3 volts but when I turn the key on I get 0 volts and I only get 5 volts at the PCM. Not sure if I am doing this correctly and help would be appreciated. Is the gen sense wire suppose to carry voltage to the alternator?

What is the generator command in the data list?? Also voltage desired vs actual? You have power at the large battery cable at the alternator?

The Gen Sense circuit is a bit weird on this system. :silly: It's what I know of as a Kelvin sense circuit. B+ is sourced from inside the alternator, passed through a fixed resistor, and sent to the PCM. What's the resistance, exactly? I don't know, it never mattered to me. :lol: On a working system, with the engine running, the Gen Sense wire will always read several volts lower than actual battery voltage.

According to SI, the Gen Sense is only there to let the PCM know if the main alternator B+ cable is open at any point between the alternator and the battery. It's a safety input, not a charging rate input.

I suggest putting everything back together/connected, and take five voltage readings, engine idling and not charging:

B+ at the battery
B+ at the alternator stud
Pin 1 at the alternator
Pin 2 at the alternator
Alternator case

What are you readings?

I found a diagram today and I guess I was checking the circuit wrong. I thought power came from the PCM to the alternator on the gen sense wire and came back through the gen field control. Kind of like a hall effect sensor. I have attached a picture of my voltage readings. The battery was low from running that is why in the picture I had less than 12 volts. And the voltages at the 2 fuse B+ on the PCM are with the key on and the others are with the van running.Thanks for the help

Tyler I checked the voltage like you asked. Also voltage is different from picture cause I charged the battery last night
B+ at the battery 12.4v
B+ at the alternator 12.4v
Pin 1 BR/GY at the alternator 0v plugged in.When it is unplugged 0.6 volts on wire and no volts on pin in alternator
Pin 2 RD/VT at the alternator 9v plugged in.When it is unplugged no volts on wire and 12.4 on pin in alternator
Alternator is grounded
Also I checked voltage at the PCM for the BR/GY with only the key on and I get 0.6 volts.

Thanks for those readings.

Pin 1 BR/GY at the alternator 0v plugged in.When it is unplugged 0.6 volts on wire and no volts on pin in alternator

...

Also I checked voltage at the PCM for the BR/GY with only the key on and I get 0.6 volts.

Ruh roh. That's the field wire for the alternator. To be clear, the engine was running when you took that reading, right?

If so, then you have to ask if the lack of field control is intentional, or because the driver in the PCM is smoked. What kind of scan tool do you have available?

Yes I took those readings with the van running.
All I have is a Actron CP9580 AutoScanner
So the field wire should have voltage? And The voltage comes from the PCM to alternator?

markjones1985 wrote: So the field wire should have voltage? And The voltage comes from the PCM to alternator?

Correct. It's a high side driver (power side switched in ScannerDanner-ese) that controls field coil strength directly. More field current -> more alternator output. The PCM will never full field that circuit, only pulse width modulate it.

For perspective, I took this off a '14 Wrangler. Same engine, same charging system.



The meter is connected to the same alternator field wire. Scan data shows the duty cycle percentage. The Voltage Sense PID is NOT the sense wire at the alternator. It's just reading fused B+. Chrysler/Dodge/Jeep likes to make things confusing.

Your reading of 600mV suggests almost no current flow on that circuit. IMO, you're down to a PCM that is intentionally not fielding the alternator, or a PCM that can't field the alternator. I asked about your scanner because a bidirectional scanner could command the field driver on KOEO to check functionality. But that's OK, we can work around it.

Any codes stored? If you scanner can read scan data, I'd like to see what the Module Supply Voltage PID says when not charging. I'd also suggest checking the field circuit for a short to ground, PCM and alternator disconnected. If that passes, I'd load test the field wire with several amps before PCM replacement.

If he has a scope or know someone that does check signal sense with scope. I think he is getting an averaged reading if it is a pwm circuit. So it may be a higher voltage coming through the circuit.

Hardtopdr2 wrote: If he has a scope or know someone that does check signal sense with scope. I think he is getting an averaged reading if it is a pwm circuit. So it may be a higher voltage coming through the circuit.

I agree that he's looking at an averaged PWM signal. But given that 7.0V equals about a 50% duty cycle on a known good vehicle, and that he found 600mV on his, I think it's reasonable to assume that whatever duty cycle that is taking place (if any) is extremely short. Not nearly long enough to field the alternator.

Could the op full field the alternator with a test light to check the new alternator output

Tyler wrote:

Hardtopdr2 wrote: If he has a scope or know someone that does check signal sense with scope. I think he is getting an averaged reading if it is a pwm circuit. So it may be a higher voltage coming through the circuit.

I agree that he's looking at an averaged PWM signal. But given that 7.0V equals about a 50% duty cycle on a known good vehicle, and that he found 600mV on his, I think it's reasonable to assume that whatever duty cycle that is taking place (if any) is extremely short. Not nearly long enough to field the alternator.

600mV could be a 12V 5% PWM signal. Or it could be a low voltage higher duty signal because of an internal problem in the PCM. AC voltage and frequency readings might help tell what it is if all the OP has is a DMM. Really need a scan tool, and ideally a 'scope too, to diag this one conclusively though.

Thanks for the help everyone. I have a friend who is going to come over Monday and help. He has a snapon scanner that can do bi directional to command the field circuit.I'll update everyone on what I find out

Just an update. It was the PCM. But I had low cylinder compression on the front left cylinder. FYI.. My dodge friend told me there is a recall on these vans for that cylinder. So it was fixed for free. So if you get oil mixing with your antifreeze that head gasket is more than likely the issue.

Thanks for all the help!

I know this post is old but couldn't he had bought an "External By-Pass Voltage Regulator Kit with Field Replacement Module" rather than a new PCM?

Sure? :huh: But the MIL would remain on afterwards. That may or may not matter depending on the owner and the local emissions laws. 

Wouldn't the Alternator Field Replacement Module acts as an alternator to trick your PCM's field control unit into thinking the alternator is still attached, getting rid of the associated fault code and no charge light in the dash?

wrote:

Wouldn't the Alternator Field Replacement Module acts as an alternator to trick your PCM's field control unit into thinking the alternator is still attached, getting rid of the associated fault code and no charge light in the dash?

Do you have a kit in mind for this application? I'd genuinely like to see specifics, if possible, for my own information.

Will the bypass trick the PCM? I think it'd depend on how the replacement module is wired. The PCM will be monitoring the field control circuit, as well as the (kelvin) sense circuit. The bypass would have to satisfy both, AND keep the actual battery voltage close to desired. Depending on how the PCM monitors the field control circuit, it may never be happy even if the actual and desired battery voltage agree.

For giggles, I looked through service info to see what kind of tolerances the PCM will have for battery voltage. I found this under the set criteria for P2503 - Charging System Output Low:

The battery sensed voltage is less than the target charging voltage, during engine operation, for a calibrateable amount of time. One Trip Fault. Generator light will illuminate.

Pretty vague. :silly: Getting the bypass to keep the PCM from setting codes like this would likely take some trial and error, IMO.

Hey man im trying to fix my mothers van for her she spent 15 grand on this thing not too many kms /miles on it and yeah oil had got into the alternator (leaked down from topping up consistently due to a bad oil pan) and in that circumstance it shorted out and i think it may have blown a safety fuse and i cant locate it as well all I know is worst case scenario it could be the voltage regulator which is in the PCM which is basically the ECU for dodge and their about 600 CAD to buy. I got the new alternator on and having same issue your having. New battery as well

Fuse is in the fuse box see pic on previous page. The owners manual will tell you where it is at if you have that in the glove box. Otherwise www.alldatadiy.com or www.eautorepair.net will have the diagrams you will need.