When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Greetings. I'm stumped.
If you read the issues and back story of this recent thread
06 Buick lacrosse, start and dies or no start
You have my story as well. More or less.
Presently I have the RAP relay code coming from the BCM and associated codes from PCM.
Ok... I go to check out my RAP relay behind the glove box and.... I don't have one!!??!!??
The bracket post is empty and no harness connector or harness for one.
Is this normal or not?
Is it a faulty BCM or something else?
I have a new one and a RLink J2534 (arrives today) getting ready to program it but first would like to be sure this is the problem and not throwing parts needlessly at it.
I can scan or scope a part or circuit for info if requested but my real question is the missing RAP relay.
I tried talking with a dealerships service guy and he said only an engineer would be able to say one way or another if some RPO were sans that component.
What to do.. what to do.
Okay so in this thread, the Lacrosse starts and dies, or doesn't start at all, or sometimes quits while running:
Originally Posted by 06lacrosse
sometimes it will crank over and just barely run a second then die. Other times like yesterday after I installed the new battery it fired right up and ran good for 10 minutes then started sputtering and died like it ran out of fuel, or the computer cut the fuel pump off possibly. It started right back up and ran long enough to drive in the garage before it did the same thing again. When I try it today the fuel pump doesn’t come on when you turn the key on so it just barely starts and dies.
Presently I have the RAP relay code coming from the BCM and associated codes from PCM.
. . . there was no mention of RAP codes or RAP in general in the entirety of the referenced thread.
Originally Posted by 02 century
Is it a faulty BCM or something else?
The BCM gets suspected for stuff all the time on all kinds of cars. My experience here tells me that if the the BCM is suspected 1,000 times across 1,000 car issues, maybe 1 might have been fixed by replacing the BCM. If this were an FCA vehicle from the last decade or two, yeah we might be talking about a bad BCM.
Originally Posted by 02 century
What to do.. what to do.
So . . . let'* start from the beginning:
Year/make/model of your car?
How many miles on it?
How many miles have you owned it?
What are the original symptoms that it had as part of the current issue?
Thanks for the great response!
Real questions I can respond to though not as complete as I would like.
It'* going to take me a while to assemble the answers so I will post them in the morning.
Greetings. I'm stumped.
If you read the issues and back story of this recent thread
06 Buick lacrosse, start and dies or no start
You have my story as well. More or less.
Presently I have the RAP relay code coming from the BCM and associated codes from PCM.
Ok... I go to check out my RAP relay behind the glove box and.... I don't have one!!??!!??
The bracket post is empty and no harness connector or harness for one.
Is this normal or not?
Is it a faulty BCM or something else?
I have a new one and a RLink J2534 (arrives today) getting ready to program it but first would like to be sure this is the problem and not throwing parts needlessly at it.
I can scan or scope a part or circuit for info if requested but my real question is the missing RAP relay.
I tried talking with a dealerships service guy and he said only an engineer would be able to say one way or another if some RPO were sans that component.
What to do.. what to do.
It began as a no start one day (but then started fine the next day and ran fine) a couple years ago. Then ran until the symptom came back spring of 24 and it sat until June of this year when I began working with it. At which point it would turn over but not start except for the first time I used my scanner to see what it would capture. It was a run stall event that showed the Cam signal present while running for about a second.
That started me chasing ICM circuit issues leading to new coils and eventually plugs. No joy.
I next worked through the fuel system draining the tank and replaced the filter and checked pressure. Ok. Still just cranked no start.
During this time I couldn't read the codes or it only had old ones because the battery had died or was disconnected for replacement with a spare to keep testing.
At some point it i don't exactly when in the sequence of events, it finally started and ran 60 sec maybe before stalling. Long enough to set codes
I had stuff unplugged or fuses out so some were for that reason and I ignored them.
The first list after running for more than a couple seconds
PCM: P1626, U1064
BCM: B3102, B3106, B3094, B1422, B1477, U1016, U1040
ICM: B3102, B3106, B3094, B1477, U1016, U1040
Okay . . . except:
. . . there was no mention of RAP codes or RAP in general in the entirety of the referenced thread.
The BCM gets suspected for stuff all the time on all kinds of cars. My experience here tells me that if the the BCM is suspected 1,000 times across 1,000 car issues, maybe 1 might have been fixed by replacing the BCM. If this were an FCA vehicle from the last decade or two, yeah we might be talking about a bad BCM.
So . . . let'* start from the beginning:
Year/make/model of your car? Buick Century limited 3.1l
How many miles on it? 74k
How many miles have you owned it? 20k
What are the original symptoms that it had as part of the current issue? See above
What codes are stored?
Currently: PCM: P0102, P1626, U1064
IPC: U1064
SIR: U1064
This is the first time I haven't seen the BCM B1477 in a week or more.🤷
Stored BCM history codes: B3102
B1477
And for the record it cranks but no start this morning. Thanks to all who take a look at this.
I went out to see what the voltage was on the BCM connectors looking for no communication or obviously weird stuff and I think* it'* all talking with the modules and circuits it'* supposed to with the exception of the RAP which clearly shows two options for that location in connector C3 pin A10.
I went down the AllDataDIY diagnostic test for the VTD once before but the Security light not going out stumped that time too.
Maybe I'll try a stopwatch for the next time and just proceed with it.
Codes from today.
I started with the P0102 thinking I still had a connector off but it had a broken wire at the connector so the 4pm san reflects that.
Maybe I have a BCM connector loose now I'll have to check it out
Otherwise back to the top. Stumped.
B1422 - Opinions vary, but it didn't come back
B1477 - RAP relay open or short to ground
B3102 - Keyless entry data circuit low voltage
B3106 - Keyless entry data circuit issue
B3094 - No response from PCM?
P0102 - MAF sensor circuit low
P1626 - Loss of fuel enable signal
U1016 - Lost communication from PCM to other modules
U1040 - Lost communication from EBCM to other modules
U1064 - Lost communication from BCM to other modules
Step 1: Remove the RAP relay and try again and see what happens. Maybe step 2 and 3 are unnecessary . . . ?
Step 2: Check all fuses with volt meter set to continuity, test from tip to tip, not test point to test point
Step 3: Check wiring and plugs connecting to the BCM, PCM, and EBCM.
Curious about B1477 DTC from BCM.
