2002 Suburban OBD2 Port Powers OBD2 Scanners; Will not connect with ECU
 

Hello everyone,

I have a 2002 Suburban that I can't access the ECU with my scanners.

These scanners work perfectly on my Jeep & VW vehicles.

I have blinking lights (Red, Yellow & Green) on the scanners (Hard Wired USB & Bluetooth Dongle) as if they are trying to communicate, but no dice when it comes to actually connecting.

Of course I need to get it inspected this weekend and I fear that the Inspection Shop will not be able to connect to the ECU either.

I currently don't have any CEL/MIL indicators or warning lights present and the engine & transmission seem to be in working order.

I do know that it has had an engine/transmission swap from a vehicle with less mileage, i.e., the body has 290k miles and the engine/trans has ~119k miles.

Thank you in advance,
L.Resendez

Update:

With the Ignition "ON", I just checked the OBD2 connector pins with a multimeter and observed the following readings:

Pin # || Voltage
02 || 00.2 - 00.4
04 || 00.02
05 || 00.03
14 || 11.28
16 || 12.42

Not sure what this means just yet, so I'm going to search around and see what they are supposed to read.

Thanks again.

Here is a video of the Ground Testing on Pins 4 & 5.


I am hearing an audible static on Pin #5.

Pin #4 gives a clean, non-static beep.

Here's a shot of my cluster with the ignition in the "on" position:

I don't see the CEL light when doing this.
EDIT: Apparently the "Service Engine Soon" is the CEL, so no little picture of the iconic engine.


Going to research what that blinking/dinging security light means.

Here's an update:

I unplugged the Rear O2 sensor (after the catalytic converter) and drove it for over 5 miles attempting to force a check engine light and it did not.

I believe something with the emissions system has obviously been bypassed.

I need to try to undo what has been done.

Any ideas?

need to check all of your fuses if you are not getting a reading at the data link connector, as for disconnecting the O2 sensor, it may not error out right away as the entire system needs to warm up as it is in an open loop mode and ignores the sensors until everything is warmed up and it goes to closed loop.
If you want an immediate CEL disconnect the MAF sensor at the air intake....

^^ thanks for the quick reply. the engine was already warm and 5 miles took almost 12 minutes to complete with a small 50 mph straight away.

before i unplugged the rear 02 sensor, i unplugged the maf thinking that it would struggle a bit and throw a fault, but it only does a half second idle change and levels out as if nothing happens with no SES light.

i unplugged what i believe is the coolant switch and the engine died immediately. plugged it back in and then disconnected a coil pack, it started up just fine and i let it run for a bit and still no SES.

could it be intentionally 'stuck' in open loop?

at this point i'm ready to just order a different ECM (VIN Programmed) off of ebay and see how that goes. i need to go pull it for the part number and also jot down the VIN but i'll order it tonight. it's less than a $100 shipped and i don't have to send the core.

it will take a few days for the ECM to arrive, so if there are any other items to test in the mean time, i will certainly try them.

thanks again :)

I've ordered the replacement ECM but have that lingering feeling in the back of my mind that it is not going to solve the issue.

A few more questions popped into my head:

If I don't have a Key Fob for this vehicle, would that in any way prevent me from properly accessing the ECM via the OBD2 port?

The orange "Security" light flashes/dings on the cluster when I have the door open. This turns off when I start the vehicle. It also turns off when I lock the doors. Wasn't sure if this is considered normal operation.

my friend used his snap-on scanner and it read the original ECM right away and pulled a few codes.

apparently i need a different scanner for this vehicle.

everything seems to be working as it should now.

thanks for the tips.