hello! i have a 2003 hummer h2 and i have a check engine light for the first time in a while. im in canada here so we dont have a auto zone to scan my codes. i first tried scanning with android obd2 and then i used my headheld diablotuner scanner, both of them got power and worked normally however both are showing there is problems communicating with the hummer. my cig light port is fine because the obd2 is also getting power just not communicating. any idea on what i can check? i read around and i do have a remote start so maybe it could be that, and or i also recently did a rear view camera with a new double din stereo.
my truck acts normally however, doesnt seem like i can pinpoint the issue

thanks!

 

Most all auto parts stores scan for free, or buy a

 

sadly i think theres some communication problem because my diablosport tuner scanner isnt even working and it works fine on my other vehicle.

 

Did you check ALL fuses?

 

The OBD2 connector only has 4 wires connected to it (see JPG)

Pin 2 is Signal, Class2 Serial on your truck, NOT CanBus.
Pin 4 is Chassis Ground
Pin 5 is Signal Ground
Pin 16 is +12V (Always ON)

So as hummerz suggests check the fuse power at the connector (it's preferable for the scan tool gets it's power from the connector)

Measure the DC Voltage between Pin 2 and Pin 5 with the Ignition On, the voltage should be around +0.5V to +2V (roughly) showing comms activity. The Class 2 Signal connects throughout the hummer mainly via Splice Packs 205, 206 and 207 this signal must be there otherwise its likely your truck wouldn't run properly. If there is not activity check Pin 2 links to Splice Pack 205 Pin D.

Check Pin 5 (GND) connects to battery ground via IP Relay Block A5 and F8 (as shown on my 04 diagram)

Some of the ELM 327 modules (copies) have been known not to work with the H2

Check your Diablo Scan Tool supports Class 2 Serial if this is the 1st time you've used it with a H2, it could be a compatibility issue. For example with a GM Tech 2 it's important to get the Model Year correct, otherwise the unit can complain about communications.



Keep us posted with what you find

 

I'm no expert but when I need to connect HP Tuners to my H2, I have to remove the fuse for the radio and amp under the hood or it will not connect.

Tim

 

Therefore someone has made a modification that you will need to reverse. Review Oceanbrave's message one more time. This is proper way to ensure you're getting obdii signals.

 

do you have an aftermarket radio and interface?

 

It was explained to me that the CANBUS signal can get interference from certain other electronic items and cause communication issues. It could be as simple as an LED bulb too. Don't know, as I said I'm not an expert.

Tim

 

I had the same issue with a DiabloSport Intune I used to use. The only way I could use it was if I first disconnected power to the remote start I had back then. That was on a Silverado I had for a while.. I have also seen where Dakota Digital (top of the line stuff seen in many restomods) gauges can interfere with other OBD devices trying to communicate. I've also read where aftermarket remote starts and even factory stuff can interfere with certain devices.