Bosch · Dryer
Bosch Dryer E03 Error Code
Condensation drain hose blocked or kinked
What this error means
E03 on Bosch condenser and heat-pump dryers means the condensation drainage hose is blocked, kinked, or installed too high. Water that should leave the condenser backs up and triggers E03—distinct from lint-related E01.
How E03 is detected
When E03 appears on a Bosch dryer, the control board has confirmed that water did not leave the machine within the programmed drain window. On Bosch WTG86401UC, Bosch WQB245B0UC, and similar variants, the drain pump runs for a fixed interval—often three to seven minutes on washers and dishwashers—while a pressure switch or turbidity sensor verifies the tub or sump is empty. If water remains, the cycle stops to prevent spin with a full tub or overflow on the next fill.
Most E03 calls are resolved without parts: trace the drain hose from the dryer rear to the standpipe without lifting above shoulder height. Restricted drain paths mimic pump failure because the impeller spins against a blocked hose or filter. Document whether the pump hums audibly during the drain step; a humming pump with no water movement points to a clogged filter or kinked hose, while silence may indicate a failed pump motor or loose wiring at the harness.
After clearing blockages, run a short cycle and listen at the drain hose for steady water flow. If E03 returns on the next load with a clean filter and straight hose, measure resistance at the pump motor connector per the service manual for your model before ordering a replacement pump assembly.
Common causes
- Drain hose looped above the 1 m maximum height in the install manual
- Kink where the hose passes through a cabinet wall
- Siphon connector at the standpipe clogged with lint slurry
- Frozen condensate line in unheated utility rooms during winter
Step-by-step fixes
- 1Trace the drain hose from the dryer rear to the standpipe without lifting above shoulder height
- 2Detach the hose at the siphon, flush with warm water, and clear the connector
- 3Confirm the standpipe is not sealed airtight—Bosch requires an air gap
- 4Run a timed dry cycle and watch for water entering the drain during the first ten minutes
When to call a technician
E03 with a verified open hose and active wall drain may indicate a failed condensate pump on plumbed heat-pump models.
Affected models
- Bosch WTG86401UC
- Bosch WQB245B0UC
- Bosch WTG865H4UC
Prevention & maintenance
- Clean drain filters and hose terminations monthly on high-use dryers to prevent E03 from lint and food debris buildup.
- Record when E03 appears in the cycle and whether it clears after a 60-second power reset on your Bosch dryer—that detail speeds diagnosis if you call service.
- Keep the model and serial number from the rating plate when ordering parts for E03; Bosch uses multiple revisions with different harness lengths and board firmware.
- Photograph wiring connector orientation before disconnecting any component while troubleshooting E03; reversed plugs on pumps and valves cause immediate repeat faults.