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Roy, import/domestic specialest
Category: Chevy
Satisfied Customers: 6175
Experience:  ASE master tech for 40 years
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Obd2/dlc unable to be scanned? Replaced TCM with used from

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obd2/dlc unable to be scanned? Replaced TCM with used from same P30 same results
JA: What is the model/year of your Chevy?
Customer: 97 chevrolet P30 6.5L diesel
JA: How old is the engine? And when was it last serviced?
Customer: 197K
JA: Are you fixing your G30 yourself? What have you tried so far?
Customer: The PCM cannot be scanned
JA: Anything else you want the mechanic to know before I connect you?
Customer: no

hello, my name is ***** ***** I will be glad to assist you. please allow me a couple of minutes to gather some basic info.


does the check engine light come on when you turn the key on???

Customer: replied 28 days ago.
check engine light does not work

ok, then you have either no power to the ecm or the ecm is no good. let me get a diagram of the powers for you to check


Customer: replied 28 days ago.
I checked the DLC and the power and grounds were all good as well as the resistances of the other pins
Customer: replied 28 days ago.
This mat not be the standard protocol and that may be the reason a scanner can't read?

no, the powers to the ecm. it is the blue connector.

I attached the picture of the blue connector and each pin. check for power at the listed pins for battery power and ignition power.


Customer: replied 28 days ago.
I also bought a used TCM from a P30 and got the same results after changing it?

as I stated before, there is likely no power going to it to make it work. you can put in as many as you want but without power it will not work. thats why we are going to diag it once repair once without throwing anymore parts at it


Customer: replied 28 days ago.
the truck run and drive fine can it do that without a PCM/TCM?

depends on what part is not powered.

did you verify powers and grounds with what I sent you??

Customer: replied 28 days ago.
I'll need to do that. How will I be able to continue this questioning if power is present?

log back in and continue. once you rate it stays open as long as you wish, otherwise it will time out.


Please take a moment and rate my service 5 stars so the site will pay me for my efforts. We only get paid when you accept our answers


Customer: replied 28 days ago.
Last question this is a non turbo the connector diagrams you sent are correct for non turbo?

yes, just check the powers and grounds listed for power.

Roy and 4 other Chevy Specialists are ready to help you

thank you

Customer: replied 28 days ago.
Still learning how to us this site. I sent a response some other way and am repeating it here. The diagrams you sent me are not for my truck. My connectors are purple a 32 pin and a 24 pin both purple.

can you send me a picture of the ecm or the number for the ecm???

Customer: replied 28 days ago.
The manual say I have a PCM but the part number on the unit from the truck 16196390 is identified as a TCM

they are together looking

have you checked all your fuses for power on both sides with the key on???

Customer: replied 28 days ago.
The plugs are side by side. All fuses checked and good.

ok, lets back up

check the ignition switch for power out on the wires with run marked

lets back up and check outputs from the ignition switch check the ones that are marked run

Customer: replied 28 days ago.
I had the steering column apart before. I don't think I can get the ignition switch out without disassembling the column. All the dash lights come on except the MIL light. when I turn the ign towards start and go out after starting.

without the check engine light on there is either a power issue to the ecm or the ecm itself.

since you said the fuses are all good. check the connectors for battery voltage at the ecm and tell me what colors have power. look at orange and red wires


Customer: replied 28 days ago.
You don't have connector diagrams for the TCM 16196390?

cannot find them still looking. I see the ecm listed but not connector diagrams. the age of it is the issue. some of them they deleted.

did you check for power to the ecm as I asked???

looking through all kinds of connectors

Customer: replied 28 days ago.
I checked some or most of the wires with the ignition off and did not pick up any voltages. Do I need to turn the ign on? I feel like I'm going to short something out? I grounded one end of the volt meter to ground and am poking the pos end of the volt meter to the connector pins.

yes, the key needs to be on

there should be at least 2 with the key off that are hot

Customer: replied 28 days ago.
The 24 pin connector orange wire is hot with key off. The pink wire on the 32 pin connector hot with key on

one thing. they do not list a non turbo for a 97. can you verify the year of this???

it is a P series step van???

Customer: replied 28 days ago.
1997 Chevrolet P30 step van Like a bread truck or UPS truck

ok, very odd with this one

you have battery and key on power. that leaves only the ecm.

this is a programmable unit since it is obd2.

I would get a reman unit and have it flashed to your vin number. after all you and me went through with this, that is the only thing left

Customer: replied 28 days ago.
I told you that I bought another TCM from the same type truck. Before I purchased it they told me it was from a good running P30 that was in a accident. It should be a functioning TCM. I can't see both TCM doing the same thing that it's the TCM's. I call a TCM remanufacturing place and they talked me out of sending it to them because the truck runs and drives.

ok, one other thing before I stand by my suggestion. check the bulb for the check engine light and see if it works. it does pass current to the ecm.

the lack of communication is the issue. a used ecm not flashed to your truck will cause a non communication from vin mis match

Customer: replied 28 days ago.
As i mentioned before as well I don't think it is a standard protocol pin configuration. I did some research online and found some must have pins for 1850 protocol this truck does not use. I was hoping you would be aware of this difference and could have directed me in the direction to find a scanner that could read the TCM
Customer: replied 28 days ago.
I pulled the dash out and checked the bulbs, visually inspected each one and they all appeared to be OK
Customer: replied 28 days ago.
The TCM I purchased was to avoid reprogramming and flashing. I got lucky and found the correct TCM for truck.

it still has to be programmed to your vin number.

what kind of scan tool are you using??

you did not happen to check the voltage to the check engine light bulb??


Customer: replied 28 days ago.
Where or who can program it to the VIN? I went to 5 different places, auto parts stores, repair places and the dealer they all said they could not read. Maybe I'll pull the dash out again an verify voltage.

thats a good idea.

again, what kind of scan tool do you have

also, any shop that has a tech 2 tool or communicator can flash it for you.


Customer: replied 28 days ago.
I never bought a scan tool because everywhere I ask if it can scan my truck they say no. As for getting it flashed if nobody can connect or communicate with my TCM how are they suppose to flash it ? That's why on got on this site in the first place, nobody can connect/communicate to/with my computer/TCM. I don't feel like I got any closer to fixing my problem so far either.

what are you using that wont communicate with the truck??? it is obd2 and any quality scan tool will work.


Customer: replied 25 days ago.
I went to truck repair businesses, auto repair business, the dealer and a transmission repair business. They had not only hand held scanners but more expensive scanners like snap-on 3500 or whatever Mac tools provides there venders. And no not any scanner will read this truck. As I said before some must use pins for the standard protocol are not used by my DLC (data link connector)/OBD2 connector

since 1996 the 16 pin as been around. federal guide lines are required that all manufactures must follow when it comes to protocall. every vehicle has the same number of pins. there is no difference in the access of info.