GMC Yukon XL 2000–2006
Common on this vehicle:LeakWarning light
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2 records state a cause or a remedy. Each record is shown as short labels in the order fault → finding the cause → correction. Press a label to narrow to the records that state it.
Read the records one by one (2)
ENGINE AND ENGINE COOLING2
Manufacturer communication2000–2006 GMC YUKON XL DENALI ・ 2023-01-06
EVAP Leak Diagnostic Service Bulletin (DTCs P0442/P0455)
1Fault
- The MIL is illuminated, and DTC P0442 (EVAP small leak detected) and/or P0455 (EVAP large leak detected) may be set in the ECM.
2Finding the cause
Possible causes
- P0455 sets because of a large leak or a purge blockage: an unseated tube connection, a damaged tube, a canister vent valve stuck open, or a purge valve stuck closed.
- P0442 sets because of a small leak, which can come from a purge valve stuck open or a canister vent valve stuck open.
Steps to confirm (in the document’s order)
- Inspect every purge connection for proper installation, and look along the lines for damage or wear; if damage is seen, confirm it with the smoke test.
- Some leaks show only under pressure and some only under vacuum, so check both ways; cycling the purge and vent solenoids with GDS2 while inspecting may show a sticking valve.
- Critical connections to check include: purge tube to purge valve (at the intake manifold), purge tube to chassis EVAP line (rear of the engine, near the transmission), chassis EVAP line to canister, and fuel tank load line to canister.
- Also check the vent valve line at the vent valve, the fuel tank load line jumper connection near the fuel tank, and that the fuel tank cap is closed properly.
- If all connections are good, check the vent valve for a stuck-open position; if the vent valve works correctly, go on to the purge valve.
3Correction
Parts
- No parts are required for this repair.
Caution
- For diagnostic instructions, DTC information and required tools, always follow the service information document for the vehicle and DTC being worked on.
Read the sentences of the record
From the manufacturer’s document
- Applies to:This bulletin only applies to vehicles with gasoline engines.
- Condition:The MIL is illuminated, and DTC P0442 (EVAP small leak detected) and/or P0455 (EVAP large leak detected) may be set in the ECM.
- Cause:P0455 sets because of a large leak or a purge blockage: an unseated tube connection, a damaged tube, a canister vent valve stuck open, or a purge valve stuck closed.
- Cause:P0442 sets because of a small leak, which can come from a purge valve stuck open or a canister vent valve stuck open.
- Confirm:Inspect every purge connection for proper installation, and look along the lines for damage or wear; if damage is seen, confirm it with the smoke test.
- Confirm:Some leaks show only under pressure and some only under vacuum, so check both ways; cycling the purge and vent solenoids with GDS2 while inspecting may show a sticking valve.
- Confirm:Critical connections to check include: purge tube to purge valve (at the intake manifold), purge tube to chassis EVAP line (rear of the engine, near the transmission), chassis EVAP line to canister, and fuel tank load line to canister.
- Confirm:Also check the vent valve line at the vent valve, the fuel tank load line jumper connection near the fuel tank, and that the fuel tank cap is closed properly.
- Confirm:If all connections are good, check the vent valve for a stuck-open position; if the vent valve works correctly, go on to the purge valve.
- Confirm:Work in this order: EVAP lines properly installed and fully seated; damage on the EVAP lines; vent valve malfunction; purge valve malfunction.
- Parts:No parts are required for this repair.
- Caution:For diagnostic instructions, DTC information and required tools, always follow the service information document for the vehicle and DTC being worked on.
Open the manufacturer’s document (PDF) ↗ The points above were read from this document.
- Remedy
- This service bulletin provides diagnostic tips/steps on testing for possible EVAP leaks in the system to correct a customer concern of an MIL Illuminated with DTCs P0442 and/or P0455 Set.
Manufacturer communication2004 GMC YUKON XL ・ 2004-05-06
EVAP Code P0442 on Various Engines Notification
1Fault
2Finding the cause
Not stated
3Correction
4.3 4.8 5.3 6.0 LR4 LU3 LM7 L59 LQ4 LQ9 ENGINES- EVAP CODE P0442. *MR
Read the sentences of the record
- Remedy
- 4.3 4.8 5.3 6.0 LR4 LU3 LM7 L59 LQ4 LQ9 ENGINES- EVAP CODE P0442. *MR

