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Randall C
Randall C, ASE MasterTechnician
Category: Ford
Satisfied Customers: 12803
Experience:  35 years ASE Master Tech, Diagnostic , Electrical Specialist
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2005 ford explorer limited: the check charging system light will come

Resolved Question:

I have an 2005 ford explorer limited. I'll be driving and I'll hear a beeping sound and the check charging system light will come up on the memo screen. I've had the battery and aternator checked and it's good. What do you think may be wrong. The battery picture will light up in red when this message appears.
Submitted: 6 years ago.
Category: Ford
Expert:  Randall C replied 6 years ago.
Chat Conversation Started
Tracer :

Hello, is the vehicle nearby that you can get me the 8th digit of the VIN # XXXXX we look at correct engine? You read the VIN from the left. the VIN is on dash, drivers side, base of windshield? I need the 8th digit from left. LMk when you can. thanks

Customer:

hold on

Tracer :

no problem

Customer:

1fmzu75k65ua61685

Tracer :

For the future if asked, you have a 4.0 litre engine Flex fuel engine. Thanks. Let me check a couple things. back shortly

Customer:

ok

Tracer :

did parts store check battery and alternator or a shop? was the test done with alternator in vehicle?

Customer:

yes

Customer:

it was checked at advanced autos and they said it was working correctly

Customer:

we also had a garage check the alternator and battery and they said it was working properly

Customer:

said the alternator was recently replaced

Tracer :

Thanks. i am going to do a bit of typing so bear with me. I will give you all the info you need to know. Coming next :)

Tracer :

Does the light/message come on and stay on all the time or.. once in awhile it comes on?

Customer:

it comes on once in awhile

Customer:

the other day i was taking my son to football practice and it came on at least 10 times

Tracer :

Thanks. Will send info next

Customer:

ok

Tracer :

In older vehicles the charging was just battery and alternator. in alot of todays vehicles, like yours, the alternator is controlled by the PCM ) powertrain control module) "computer" . You could drop into most any shop and the alternator tests ok but.. the PCM has detected a problem and may not be alternator or battery at all. I never like to tell customers this but.. you could have a PCM going bad. the other thing is the shop MUST test alternator when light/message is on. If not, it will pass all tests. the next step unfortunatley is to have a shop hook a full system scanner. they can view PCM data and charge data as well. Yes,, it may be charging all the time and you will have no problems even with light on but the light means something has been detected. It can not be ignored. if older truck, i would say bad alternator but your vehicle is different. The PCM controls the regulator inside the alternator. It can be a little tricky to diagnose when problem/light occurs. yes, you could? have PCm going bad. rare? yes, but can happen. below is a very formal description of the charging system in technical terms.

Tracer :

Powertrain Control Module (PCM) Controlled Charging System

Overview

The PCM-controlled charging system provides many additional benefits over the current integral generator regulator system. The first benefit is improved battery life. In an integral generator regulator system the regulator set point is established by a temperature sensor in the regulator which estimates battery temperature. In a PCM-controlled charging system the regulator voltage set point is determined by the PCM and communicated to the regulator through the generator regulator control (GENRC) circuit. The PCM uses an algorithm to estimate battery temperature. Improving baffery temperature estimates will reduce battery damage caused by over- and undercharging.

The second benefit is improved engine performance. Whenever the PCM senses a wide- open throttle (WOT) condition the PCM will momentarily lower the regulator voltage set point. This reduces the torque load of the generator on the engine and improves acceleration. The PCM has a calibratable time limit on this reduced voltage feature. This is to prevent the generator output from being cut back for an extended WOT period which could cause battery discharge.

The third benefit is improved idle stability. In response to the PCM's GENRC signal the regulator uses a generator load input (GENLI) signal to provide feedback to the PCM. The GENLI signal provides the PCM with charging system information. Specifically it lets the PCM know when the charging system receives a transient electrical load which would normally affect idle stability. Because the PCM can anticipate additional loads actions can be taken to minimize idle sag. The PCM can choose to either reduce the regulator set point or increase engine idle speed~ both of which are calibratable features. In order to establish whether the regulator is accurately maintaining the desired voltage set point~ the regulator uses a charging system voltage line to sense battery voltage.

The fourth benefit is reduced cranking efforts. The PCM can reduce the mechanical load on the starter by initially commanding a low voltage set point. This may improve start times.

If the PCM detects a charging system error it will broadcast a low voltage telltale (ON) network communication message which tells the cluster to illuminate the charge indicator. The charge indicator will be illuminated if the PCM fails to see a signal on the GENLI circuit for a time period greater than 500 milliseconds. This telltale command will also be used to indicate over-voltage conditions detected by the PCM-controlled generator.

Each time the ignition switch is cycled to the run position the instrument cluster will initiate a bulb check by illuminating the charge indicator. It is the PCM's responsibility to issue a low voltage telltale (OFF) command if the charging system is functioning properly. This message should be sent during the network initialization in the voluntary phase (250 milliseconds to 450 milliseconds after the ignition switch is cycled to the run position). If a low voltage telltale (OFF) network communication message is not received the instrument cluster will continue to illuminate the charge indicator indefinitely.

Customer:

how much does this part cost

Customer:

the pcm for my type of vehicle

Customer:

i just bought it off from a used car lot. I only had it for two weeks and this is already showing up. I still have a 30 day warranty on the vehicle

Customer:

i would like to get this replaced if i can. i have the vehicle financed through the bank for 48 months. Can this be fixed? Or did I buy something that's unrepairable?

Tracer :

By no means can i say this is the problem 100% but by your description and tests done so far, it is looking like possibility. Since alt was changed one time before, someone may have been chasing a problem. the PCM new is not cheap. May? be able to find aftermarket but hard to match #'s/. each area prices different so my info may not be at 100%accurate but should be close. labor is nothing, its the part

Tracer :





























Engine Control Module
ECM
Auto Trans5U7Z12A650BJA$869.98










Order By Stamp Number.





















LaborSkill
Level
Mfg.
Warranty
Standard
Engine Control Module
ReplaceB0.50.6

Customer:

Thank you Tracer, I have talked to several people and searched on the internet if anyone else has had this problem and it's the same thing that you mentioned to me. I appreciate the help. Thanks,

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