Applicable Systems
OBD-II
Symptoms
EGR system flow below expected level during EGR command test; ECM detects insufficient EGR flow.
Possible Causes
- EGR valve not opening fully
- DPF differential pressure sensor faulty (if used for EGR monitoring)
- EGR passage partially blocked
Troubleshooting Steps
- Step 1: Command EGR valve open with scanner and monitor response
RPM drops slightly when EGR opens - Step 2: Check EGR temperature/pressure change when valve opens
Temperature/pressure changes - Step 3: Inspect EGR passages for carbon buildup
Passages clear - Step 4: Clean or replace EGR valve
EGR flow within spec - Step 5: Clear code and perform drive cycle for EGR monitor
EGR monitor passes
How to Reset
Clear with OBD-II scanner; requires drive cycle (steady cruise, 30+ mph, 2+ min).
Common Replacement Parts
- EGR Valve (OEM spec)
Frequently Asked Questions
- Q: What is EGR monitor?
OBD-II self-test that verifies EGR system operation. Performed during specific driving conditions. Fails if EGR flow doesn't match expected when commanded.
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Source: SAE J2012 standard DTC list + OBD-II portal
Category: OBD-II
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