A Corvette get this message"Service Electrical System" on display from time to time last two years . He has put his car in workshop snd the replaced the alternator with a GM genuin one but the
error massages appear again and again . When he push his car a bit the message appear in the dispaly .
I connected my SnapOn Edge scanner and we took a drive together when logged the signals .
What I noticed is the the IGN1 votage drops several times from approx 14 volt to close to 12 volt (see first plot) . Why I do not know.
I also noticed both banks goes very lean during the trip (vaccum leakage or clogged injectors , I do no not known yet )
The bank 1 and 2 front O2 sensors seems to behave normally

I think the ECM is trigging the message"Service Electrical System" , but I am not certain on this

My next step is to connect my 4 channel scope to the battery (1) and the the FUSE 9 (2))and view the voltage on the scope when he is driving the car in order to verify the the voltage drop scown on my scanner .

Does anyone has some good advice on troubleshooting this issue on C6 ?

Thanks in advance from Norway



Intalling this into FUSE 9 engineroom fuse box to measure the IGN1 voltage to ECM






Voltage on battery when idiling seems normal

 

Nice to see you back !!…have you tried swapping Ignition 1 relay with say the Rear Defogger or another 4 pin relay…maybe there is high resistance on the relay load contacts…yes, I’d do a voltage drop from battery positive to Fuse 9…the ignition relay feeds many things like O2 sensor heater, IAT, EVAP Purge…I would also voltage drop the B+ lug on the fusebox from battery positive to the lug itself and then to the stud…maybe loose or high resistance there…I’ve seen that one time…and then it’s always a good idea to voltage drop the charging system…with your scan tool I would go into the BCM and check Ignition 1 voltage there also.

 

CHARGING SYSTEM MESSAGES
The DIC displays a charging system message the when the following occurs:
- The engine control module (ECM ) detects that the generator output is less than 11 volts or greater than 16 volts. The DIC receives a message from the ECM requesting illumination of the charge indicator / charging system warning message.
- The IPC determines that the system voltage is less than 11 volts or greater than 16 volts. The IPC receives a message from the body control module (BCM) indicating the system voltage.

BATTERY SAVER ACTIVE
The DIC displays the BATTERY SAVER ACTIVE message when the body control module (BCM) reduces or disables the performance of some vehicle systems in order to reduce the load on the charging system. The DIC receives a message from the BCM requesting illumination.

BATTERY VOLTAGE HIGH
The DIC displays the BATTERY VOLTAGE HIGH message when the IPC determines that the system voltage is greater than 16 volts. The IPC receives a message from the body control module (BCM) indicating the system voltage.

BATTERY VOLTAGE LOW
The DIC displays the BATTERY VOLTAGE LOW message when the IPC determines that the system voltage is less than 11 volts. The IPC receives a message from the body control module (BCM) indicating the system voltage.

SERVICE CHARGING SYS
The DIC displays the SERVICE CHARGING SYS message when the ECM detects a malfunction with the generator output. The IPC receives a message from the ECM requesting illumination.

 

Thanks Rob

I will carry out you good advices and swap the IGN1 relay and Rear Defogger relay after I have carried out my the scope measurements first .
My first thought is burned contact set in the IGN relay causing voltagedrop in the supplied ECM voltage .
If I compare batteryvoltage with the voltage supplied to Fuse 9 using my fusecurrent device It should be possible detect this voltage drop .
I will also inspect the B+ lug nut as you recommend me to

He get the message "Service Electrival System" several times during this short driving trip.
I cleared all his DTC's prior to the trip and noticed both P0171 and P0174 appeared again during this short trip .
The front O2 sensors seems to operate fine between 0.1-0.9 volt during the driving , may a vacuumleak causing this .

This car will be around next week one day and will report back my findings

 

Just look at your fuel trims…if elevated beyond 10% run the engine at 3000 RPM and if short term and long terms decrease you have a vacuum leak…if not and this code set when you had a low voltage condition the injectors are fed off the relay…if low voltage at the injectors this may be why you are seeing both banks lean…try current ramping one of the injectors or all 8 if you have 2 of the “fuse buddies”…you should see around 900 milliamps.

 

Thanks again Rob on your good advices .

I do have a second injector harness I used when I checked my own LS injectors on my C5 .

I will install this hardness on one injector on bank 1 or 2 and the currentbuddy on Fuse 9 and use a third channel on battery voltage monitoring while the engine is rev to 3000 rpm
while I observe the behavior of the SFT and the LFT behavior .
I hope (and guess) a voltage drop will appear on the 19 year IGN1 relay 44 when doing this .
If so I will swap relay 44 with relay 40 (rear defog) and verify with similar measurements

 

Had a visit today of this 2006 car and did some scope testing and logging av signals .
My guess/hope was a voltage drop on the IGN1 signal was caused by "worn" contact set of relay 44(IGN1)
I do not know where the IGN1 voltage are measured(by the scanner) and indicated with several voltage drops on my trip on th 20th of June





I measured the battery voltage and voltage at the Fuse 9 (with my fusebuddy )



Like this

and this



Currentdraw of injector 1 was about 990 mA (my LS1 are about 1.1 amp so this current seems ok




Battery voltage approx 14,2 volt and Fuse 9 voltage approx . 14.0 volt steady all the time on my scope when the car was reved up to 3000 rpm until the "Service Electrical System " appeared again after a few minutes period





As my TopDon shows the LFT goes High very fast and stay high until the rpm drops down to idle . SFT stays normal all the time in my opnion



Closer look in a combined view first part of logging





Closer look in a combined view last part of logging




Should the LFT drop down if there was a vacuum leak ? What could cause the LTF stay this high all the time .
It seems like the APP /TPS sensors behavior follow LTF in both banks ....

I swapped both the IGN1 relay(44) wilth relay 40(rear defog) as you suggested , but it it made no difference .
I noticed the RUN CRNK relay also ended up in a IGN 1 voltage on the schematic and swapped this relay too , but the " Service Electrical System" still appeared when idling 3000 rpm some few minutes .
This indicated to me that these relays seems to work correctly .

Can this " Service Electrical System" shown in the DIC be created by the BCM module ?
Why does the LTF goes high and stay this high when RPM is at 3000 ?

If you have some good advices on what to do next I would appreciate it you have some .
I may be missing something

 

Since you have a scope I would check all 3 wires at the alternator while the car is running and see what it looks like when the message pops up.

 

Thanks , will do so .

I will monitor BATT, S , F and L Terminal next attempt during message apperance

I have done this on my C5 (photo)

 

Do you have any advice on why the LFT on both banks go into the roof (+24) before the engine hit 3000 on the way up and does not lower before the RPM goes down due to the accelerator pedal position is reduced ?
Could a very big vaccum leak cause this kind of fuel trim behavior ?
I thought LFT should drop when RPM was raised to 3000 due to more trottle air compared to any leak air coming into the intake .

 

If LTFT increase as the RPM is increased that is either a fuel delivery or MAF issue…vacuum leaks are more pronounced at idle because of higher manifold vacuum…as TB is opened manifold vacuum decreases so it will not be so pronounced at higher RPM.

 

Thanks for your advice .
That was my understanding too of how it works regarding vacuumleakage .

I will check the fuelpressure on the fuel rail and see how the pressure behave when the idling RPM is increased to 3000 .
Maybe the filter needs to be replaced

I see the MAF sensor signal behave similar to the APP/TPS sensor signal , but maybe a MAF sensor cleaning should be carried out( Has probably never been carried out....)

 

This is my alternator with NO LOADS...blue is the red/white horn-alt sense fuse, red is the gray duty cycle wire and I'm around 46-47 % duty cycle and with a DVOM I'm reading 6-7 volts so since a DVOM reads the "average" voltage this is what you will see...the green trace is the orange wire which is the alternator "turn on" signal which reads 4.94 volts...looks like your duty cycle is only at 9 volts...should be close to system voltage...I don't know which one is turn on but it looks like it's close to system voltage...I don't know if this scope capture is a C5 or C6 ???

 

Thanks for your scope picture of your alternator signals .

I do not know why my duty cycle only have approx 9 volt .
I think I have do new measurement tomorrow on my car to sort it out right away

 

Today this nice car visited me again


I did hook up a fuelgauge on the scradervalve on the fuel rail , Connected S(batt sense),F(duty cycle) and L(Gen turn ON) to my scope .
Did also connected my SnapOn scanner to the OBD port of the car to log the signals and view them in Shopstream later on my desktop.



Fuelpressure approx 58 psi on idle


When rpm icreased to 3000 rpm the fuelpressure kept very steady on 58 psi , no pressuredrop that should result in the increasing LTF on both sides
seen on the Shopstream curves below .

Did take a quick check on the secondary voltages with my GTC 505 , buth the where all stable on same voltages


As the the Shopstream show both LTF's follow the rise of the rpm .
I notice a change in bank 1 and 2 O2 sensorsignals at the same time , why ?
They seems to be less responsiev with the increased rpm .

These sensors are 19 years old and I recommende the owner to replace them with new sensers .
I guess the fuelpump seems to be OK when the fuelpressure keeps steady .
My next suggesteion is to perform a cylinder balance test to see if all the injetcors has the same pressure using my Tech2 scanner .

Do you have any other advises or suggestions ?








After I adviced the C6 owner to check the BCM contats/plugs in passenger footwell as described in this CF post , the
"Service Electrical System " has not appeared again . .
I think (hope) his actions caused better contact within the pins og these plugs due to his movement of the plugs .
Nothing showed up on my scope during the testing today


https://www.corvetteforum.com/forums...g-gremlin.html

 

I did a test on my 2000 LS1 engine later today with 3000 rpm . My LTF behave more normal and did not exceed 8 while the engine was running at 3000 rpm .
Is a cylinder balance test on the C6 engine next to go to very if any of the injectors are clogged and causing this high LTF values ?

 

O, trying to figure out what you’re doing…so your fuel trims increase at 3000 RPM ??…if so either fuel delivery or a MAF issue…you can’t always go by fuel pressure as fuel VOLUME is more important…just do an injector balance test with your scan tool.

 

Have you checked the Alt. for belt slippage.? This will cause a reduction in power output of the Alt. Look at the wear indicator on the belt tensioner. Your belt may be stretched to the point where it starts slipping.

 

The engine rpm was increased from approx 700 rpm to 3000 rpm. The fuel manifoil was 58 psi during this session . The LT (both) goes straight to 20 (or above) as the shopstream shows , the MAF , APP and the TPS signal behave the same way .
Do you think this can indicate clogged injectors and a cylinder balance test will disclose the affected injectors ?

I will get alternator belt get checked for belt slippage

 

Finally this car came back to my placed and I planned to perform a Fuel Injector Balance test with Tech2 .

First I checked all injectorcoils and they seemed to be close to each other regarding resistance measured with my multimeter



I then connected my gauge to the manifoil and the pressure was zero as the photo show.

I asked the driver/owner set the Ignition ON (pressing the ACC button once):
No pressure build up on th manifoil when he did this ....

First Question : Should not the fuel pump started and run 2 sec when he did this ?
Second Question: How do I get started the fuelpump in order to perform the , I then went through the Tech2 menu and found the Injector Balance test .

But because I could not get the fuel pump to run and build pressure with Engine OFF as mentioned above
my Injection balanse test failed .

I have carried out this test on my C5 and the pump runs for 2 sec with ignition key ON , is it not similar with C6 and Accessory Mode ON ?

I hope someone familar with Corvette C6 Fuel Injector balance test can tell me what I am missing or failing on.
I have linked below to a screenvideo of my Tech2 steps .
I tried to use Engine Output Controls to start the fuelpump this way , but ended up with a low voltage message on Tech2 screen (measured battery voltage to 12.35 Volt)
The car fires up and build fuelpressure to 58 psi on every normal start