2002 GMC Jimmy engine light comes on and off

The PO418 code relates to a relay inside the PCM which you have already swapped, so we can ignore this for now as it is probably caused by the other fault !!

I can supply a test sequence for this DTC PO405 if you want to try it !!

DTC P0405: EGR POSITION SENSOR SIGNAL VOLTAGE EXCESSIVELY LOW
NOTE:For circuit reference, see WIRING DIAGRAMS article.

Circuit Description
The PCM monitors EGR valve pintle position input to ensure that valve responds properly to commands from PCM and to detect a fault if the pintle position sensor circuit is open or shorted. If PCM detect an excessively low EGR position sensor signal voltage, this DTC will set.
Code Enable Criteria
Conditions for running DTC:
Ignition voltage is greater than 11.7 volts.
Engine is running.
Conditions for setting DTC:
EGR position sensor voltage is less than 0.14 volt.
Conditions present for 5 seconds.

ran it a second time
same things happened upon start up.

Here is the diagnostic readout

DTC Information

Stored Codes
P0300 Multiple Cylinder Misfire Detected

P0405 EGR Position Sensor Circuit Low Input

P0418 Secondary Air Injection System Relay A Control Circuit

Pending Codes
P0300 Multiple Cylinder Misfire Detected

P0418 Secondary Air Injection System Relay A Control Circuit

P0405 EGR Position Sensor Circuit Low Input


Diagnostic Information

Freeze Frame Information
Parameter Description Value
DTC for which Freeze Frame was Stored P0300
Fuel System 1 Status Open Loop
Fuel System 2 Status Open Loop
Calculated LOAD Value 12.94 %
Engine Coolant Temp 150.80 °F
Short Term Fuel Trim - Bank 1 0.00 %
Long Term Fuel Trim - Bank 1 -1.56 %
Short Term Fuel Trim - Bank 2 0.00 %
Long Term Fuel Trim - Bank 2 -0.78 %
Intake Manifold Absolute Pressure 15.99 inHg
Engine RPM 1,347.00 rpm
Vehicle Speed Sensor 1.24 mph
Air Flow Rate Mass Air Flow Sensor 2.93 lb/min
Absolute Throttle Position 7.84 %
Monitor Information
Monitor Name Monitor Icon Status
MIL ON
Misfire Monitoring Complete
Fuel System Monitoring Complete
Comprehensive Component Monitoring Complete
Catalyst Monitoring Not complete
Heated Catalyst Monitoring Not Supported
Evaporative System Monitoring Not complete
Secondary Air System Monitoring Not complete
A/C System Refrigerant Monitoring Not Supported
Oxygen Sensor Monitoring Not complete
Oxygen Sensor Heater Monitoring Not complete
EGR System Monitoring Complete

Hey Jackie/Jess and MR Jackie..LOL. Did you see my last 2 post's ?? anyway as you said it is late .. will try again in the morning !! I need you to clean the MAF sensor it sems to be running rich (overfueling) .. also I am including these test's if you could try them in the morning ? these tests are designed for a GMC code reader do not worry if your reader will not perform these test .. just do the voltage test's .. DTC P0405: EGR POSITION SENSOR SIGNAL VOLTAGE EXCESSIVELY LOW NOTE:For circuit reference, see WIRING DIAGRAMS article. Circuit Description The PCM monitors EGR valve pintle position input to ensure that valve responds properly to commands from PCM and to detect a fault if the pintle position sensor circuit is open or shorted. If PCM detect an excessively low EGR position sensor signal voltage, this DTC will set. Code Enable Criteria Conditions for running DTC: Ignition voltage is greater than 11.7 volts. Engine is running. Conditions for setting DTC: EGR position sensor voltage is less than 0.14 volt. Conditions present for 5 seconds. Diagnostic Procedures Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step. NOTE:If DTC P1635 is set, diagnose DTC P1635 first. Go to DTC P1635. Turn ignition on, with engine off. Using scan tool, observe EGR position sensor voltage parameter. If scan tool indicates that EGR position sensor voltage is less than 0.14 volt, go to step 4. If scan tool does not indicate that EGR position sensor voltage is less than 0.14 volts, go to next step. Observe the FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Operate vehicle within the conditions for running the DTC or as close to FREEZE FRAME/FAILURE RECORDS data observed. See CODE ENABLE CRITERIA. If DTC resets, go to next step. If DTC does not reset, problem is intermittent. Turn ignition off. Disconnect EGR valve harness connector. Connect a fused jumper wire between EGR valve harness connector terminals "C" (Brown wire) and "D" (Gray wire). See Fig. 5. Turn ignition on, with engine off. Using scan tool, observe EGR position sensor parameter. If scan tool indicates that EGR position sensor is about 100 percent, go to step 10. If scan tool does not indicate that EGR position sensor is about 100 percent, go to next step. Disconnect fused jumper wire. Using a DVOM, check voltage between EGR valve harness connector terminals "B" (Black wire) and "D" (Gray wire). If voltage reading is about 5 volts, go to step 9. If voltage reading is not about 5 volts, go to next step. Turn ignition off. Check for open or high resistance in Gray wire between EGR valve and PCM. Repair as necessary. After repairs, go to step 15. If circuit is okay, go to next step. Check for short to ground in 5-volt reference circuits from other components. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 15. If circuits are okay, go to next step. Connect DVOM between EGR valve harness connector terminals "B" (Black wire) and "D" (Gray wire). Observe voltage while disconnecting all sensors, one at a time, that use a 5-volt reference signal. A change in voltage indicates the faulty component. Replace that component as necessary. After repairs, go to step 15. If no problem is found, go to step 11. Turn ignition off. Check for short to ground, high resistance or open in Brown wire between EGR valve and PCM. Repair as necessary. After repairs, go to step 15. If circuit is okay, go to step 11. Turn ignition off. Check for short between Brown and Red wire at EGR valve harness connector. Repair as necessary. After repairs, go to step 15. If circuits are okay, go to step 12. Check for poor connections at PCM harness connector. Repair as necessary. After repairs, go to step 15. If connections are okay, go to step 14. Check for poor connections at EGR valve harness connector. Repair as necessary. After repairs, go to step 15. If connections are okay, go to next step. Replace EGR valve. After replacing EGR valve, go to step 15. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE under PROGRAMMING. After replacing EGR, go to next step. Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Operate vehicle within the conditions for running the DTC. See CODE ENABLE CRITERIA. If DTC runs and passes, go to next step. If DTC resets, go to step 2. Using scan tool, observe the stored information and Capture info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS. If no DTCs are displayed, system is okay. figure 5)

let me know

Hi Dave
Sorry I haven't responeded
We have been having major problems with our internet.
We couldn't find the problem so took it to a dealership to find out what is wrong.
They still have it
They checked everything and thought it was an injector and replaced everything but that didn't help..
They believe it iis a component in the heads so they are taking the heads apart to find exactly what is wrong.
Thanks
We will let you know what they find

Hello. one of my first post's to you was to have a compression test on the heads !.. but what made me change my mind was the fault seemed to be there one minute and then vanish for a while only to come back again ?? this does not sound like a bad valve or injector leak etc.. I would be very interested in your final fix please keep me posted on developments ? Thanks

how is the oxygen sensors?