Diagnostic Procedures
- Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
- Check if DTC(s) P0171, P0172, P0174 or P0175 is also present. Diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
- Turn ignition on, with engine off. Using scan tool, select ENGINE 1 and note MAP display. If reading is greater than 75 kPa (95 kPa at sea level), go to next step. If not, go to step 9).
- Disconnect vacuum hose to MAP sensor. Connect a hand-held vacuum pump to MAP sensor. Slowly apply vacuum (up to 20 in. Hg) to MAP sensor. Note MAP display on scan tool. A 4kPa drop in MAP reading should result for every inch of vacuum applied. Watch for a skip or jump in sensor reading. If reading skips or jumps, go to step 9). If sensor reading changes smoothly, go to next step.
- Apply 20 in. Hg to MAP sensor. If MAP sensor reading is 34 kPa or less, go to next step. If MAP sensor reading is greater than 34 kPa, go to step 9).
- Remove vacuum source from MAP sensor. If MAP sensor reading returns to original reading, go to next step. If MAP sensor reading does not return to original reading, go to step 9).
- Reconnect MAP sensor. Start and idle engine. Using scan tool, command EGR valve from zero percent to 70 percent (in 10 percent increments). Note MAP sensor value. MAP value should increase about 4-8 kPa for every 10 percent increase in EGR. If MAP value increases as specified, check for intermittent restrictions, blockages and/or leaks at vacuum source/line. If MAP value does not increase as specified, go to next step.
- Check EGR valve and vacuum passages for restrictions and/or blockages. Repair as necessary. If vacuum passages are okay, go to step 10).
- Replace MAP sensor.
- Replace EGR valve.