Well, bought VA truck for my son and it failed inspection when I registered in NC for no SES light when ignition turned on, vehicle not running. So I took the dash apart and checked voltage from pin 2 (tan/wht) to pin 7 (pink). I get 12 volts between the 2 with ignition on, not running. Cluster removed. Since this is an LED I checked between anode and cathode with a multimeter set to check diodes. Reading is lower on SES (.757) than on other LEDs (.964).

I plugged in my scan guage and it showed P0650 fault (Malfunction Indicator Fault). (I think this fault has been present and stored since the problem has been present since I went to get it inspected. Cleared fault and plugged cluster back in.The fault returned after a couple of starts, the SES never lit. I removed the cluster again and reset the fault. It has not yet returned.

My question is, does the PCM recognize that the light does not come on through the readings (voltage or amps) running through the circuit on the instrument cluster then indicates the P0650 fault? Since I am getting voltage across 2 and 7, I am hoping it is a bulb (diode,LED) issue and not a computer problem.

Another thing I noticed was when I first plugged the scan guage in, it had no power. I replaced the lighter fuse which had blown. It was bad when I first got the truck and it had no lighter. I put a new a lighter in. I am not sure if my son tried the lighter or not, but I am guessing he did. But it was blown again. Scan Guage worked then and is now.

I have another cluster coming in case it is a bad LED. I am not sure. Any suggestions on what else to check?

Related or a separate ? - I have no indication Cruise Control is engaged and it does work. Is there a light to indicate this? I have had it on other vehicles (CHevy, Ford, Toyota)

THANKS, George

 

No, there is no cruise control indicator on my truck, either. Sorry I can't help with the first part.

 

Thanks rriddle3, I wasn't sure and thought it might be a related fact. Much appreciated

 

On the CEL, sounds like you have gone through the proper diagnostics. I am assuming that the entire I/C isn't inoperative, but just the CEL. If that is correct, then the 'Gauges' fuse is ok and the wiring is not suspect.

If, after replacing the cluster the CEL is still inop, then the next course of action would be to replace the PCM.

Here is a link to the full diagnostic flow chart for the P0650 - Courtesy of HotRodLane.cc

 

GM runs power to all sensors and then runs the ground through the puter. The puter controls the ground, and it knows how much power is sent to the sensor. It reads the voltage coming from the sensor, compares it to the known voltage and goes from there. So yes, it is possbile that the code is due to the fact that the light isn't working.

The O2 sensors are different.

 

Thanks swartlkk and Hanr3, I appreciate the help and am just waiting for the I/C to arrive. BTW, I had also put 12 V to pin 2/7...no light then either. I am hoping just an IC

 

UPDATE -

Well, installed a replacement I/C and now the SES light is functioning as it should. HOWEVER, when I took it in for re-inspections the state OBDII link did not get a ready condition.The read out the inspection station gave me reads as follows:

Engine misfire - Ready
Fuel System Performance - Ready
Comprehensive Component - Ready
Catalytic Converter Efficiency - Not Ready
Heated Catalyst - Not Available
Evaporative Emissions Control System - Not Ready
Secondary Air Ayatem - Not Ready
AC Refrigerant - Not Available
O2 Sensors - Ready
Heated O2 Sensor - Ready
EGR Flow - Ready

Well I am at a loss. Everything passed on initial inspection EXCEPT the SES with a P0650 code. I did change instrument clusters and disconnected neg of battery during the process (10 - 15 mins). Drove the Blazer about 100 miles today (after second failure) and my scan guage reader still says NOT READY.

Any ideas? [:@]I am a little frustrated as problems seem to be boncing around. As for wiring etc, the ONLY ones I tinkered with were the connector at the instrument cluster.

New Problem?

Thanks for the help in advance, everyone is supportive and it is appreciated!!!!!!!!

 

There is a very specific set of requirements for a complete drive cycle. A complete drive cycle must be completed before all of the system monitors switch to ready. The Catalytic Converter Efficiency and Secondary Air System being two of which take a very specific sequence of events.

Generally, a complete drive cycle can be completed in 10-20 minutes, but don't attempt it on a busy road! LOL

Here's the steps: GM OBD2 Drive Cycle - Courtesy of OBDii.com

As the link states though, the catalyst monitor may take a few cycles to complete. The Secondary Air System isn't mentioned due to it not being a common feature on most GM OBD2 vehicles, but the test will be completed over the course of the drive cycle.

 

Thanks Kyle....I just read the cycle info....will try later today!

Another factor?????

I have had the scan guage II hooked up since I reset the P0650 code last night. I did not disconnect it until just before the tech hooked up for the inspection. A frined at work had been told the state computer can "tell" when a code has been reset if a driving cycle has not been completed before the test. My next/newest question is, should I leave the scan guage II disconnected from the Blazer until they check it again? Truck is running just fine and everything is working no SES due to a fault, etc....

Again, thanks Kyle!

 

Any time you reset a code, it resets the PCM. So any readiness monitors are reset to not-ready, all of the fuel trims are reset, all of the shift algorithms are reset, everything resets back to default state. So basically the entire truck needs to relearn all of it's peak operating values all over again as well as adapt to your style of driving (to a certain extent). That is why it is much better of an idea to make a repair and see if the codes go away on their own than to reset or clear them. Sometimes it is necessary to clear them to validate a repair, but a drive cycle needs to be completed to get all of the monitors to their ready state again.

Also, I do not think it is necessary to disconnect your scan guage so long as you aren't resetting the PCM without doing a drive cycle and verifying that all of the monitors are in their ready state. You should be able to just disconnect the scan guage and plug in the inspection test cord.