Mechanics

CHEVY CHECK ENGINE LIGHT BLINKING

1996 Chevrolet S-10

Computer problem
1996 Chevy S-10 6 cyl Two Wheel Drive Automatic 150000 miles

checked for codes and got P0140, reset code and now there are none. Check engine light blinks. Engine run rough at an idle. Problem started after a long driving distance and when I noticed the idle and when I accelerated it sounded like it was popping back thru the intake
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Brickclerk
December 19, 2008.




Blinking check engine light is a sign of misfire
check it for tune up

also remove and check EGR valve if stuck open
DTC P0140 - HO2S INSUFFICIENT ACTIVITY BANK 1, SENSOR 2

NOTE: For circuit reference, see DTC P0137 schematic.

Circuit Description
VCM provides about 0.45 volt reference to Heated Oxygen Sensor (HO2S). HO2S sensor signal voltage varies from about one volt when exhaust is rich to about 0.1 volt when exhaust is lean. VCM reads and stores sensor voltage information and evaluates the voltage samples to determine amount of time sensor voltage is out of range. If HO2S voltage is out of predetermined range, DTC will set.
Conditions required to test for DTC are: ? No ECT, IAT, MAF, MAP or TP sensor DTCs set.
? No EVAP system DTC set.
? No other DTC tests in progress.

Diagnostic Procedures
1. Perform On-Board Diagnostic (OBD) System Check. Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step. 2. Start engine and allow it to reach operating temperature. Place gear selector in Park or Neutral, and apply parking brake. Increase engine speed to greater than 1200 RPM for 2 minutes. Using scan tool, read LOOP MODE. If scan tool displays CLOSED LOOP, go to step 5). If scan tool does not display CLOSED LOOP, go to next step. 3. Turn ignition off. Disconnect HO2S connector. Connect a jumper wire between HO2S harness connector signal and ground circuits, and chassis ground. Turn ignition on, engine off. Read HO2S BANK 1 SENSOR GROUND voltage. If voltage is less than 0.2 volt, go to step 7). If voltage is 0.2 volt or greater, go to next step. 4. Remove jumper wire. Turn ignition off. Reconnect HO2S connector. Disconnect Blue VCM connector. Connect a test light between Blue VCM harness connector signal circuit and battery voltage. If test light illuminates, go to step 6). If test light does not illuminate, go to step 9). 5. DTC P0140 is intermittent. If any additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS. 6. Check HO2S harness connector signal circuit for open. If open is found, go to step 11). If no open is found, go to step 8). 7. Check HO2S for faulty connection. If faulty connection is found, go to step 11). If connection is okay, go to step 10). 8. Check VCM for faulty connection. If faulty connection is found, go to step 11). If faulty connection is not found, go to step 12). 9. Repair open ground circuit and go to step 13). 10. Replace HO2S and go to step 13). 11. Repair circuit as necessary and go to step 13). 12. Replace VCM. Program replacement VCM using required equipment. Go to next step.

13. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter DTC P0140. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, return to step 2). 14. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.
Diagnostic Aids
Check for faulty connections or damaged harness. Check for faulty HO2S heater. Observe scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

BMRFIXIT
Dec 19, 2008.


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