Quick symptom overview
Bosch WAT / WAW / WAS / 300–800 series front-loaders post E18 when drain time expires. Two sensors lie: the drain pump (water actually leaves) and the analog pressure sensor on an air-trap / pressure chamber (the board thinks water left).
Pump path: coin filter packed, impeller locked, winding open, non-return valve stuck, standpipe too high. Pressure-chamber path: the small hose from the outer-tub air trap is pinched, waterlogged, or the trap is full of lint and soap—E18 with a drum that already emptied. E23 is the electrical pump fault (open winding / no drive), not a timeout.
LG’s drain timeout is a different brand’s same idea: LG OE drain error. Do not treat E18 like dishwasher AquaStop: Bosch E15 base pan.
Safety: Unplug before the pump filter or pressure hose. Residual tub water dumps from the Bosch drain door—pan and towels. Do not blow hard into the analog sensor. Live 120 VAC at the pump during drain.
Step-by-step diagnostic hierarchy
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Separate E18 from E23 / E17 — Photograph the code. E23 = pump electrical. E17 = fill/flow. E18 = did not empty in time.
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Look at the glass — Standing water = mechanical drain until proven otherwise. Empty drum + E18 = pressure chamber / sensor.
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Drain door / pump filter — Emergency drain hose first, then the coin trap. Hair, coins, and Florida sand lock the impeller.
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Hose and standpipe — No kink behind the cabinet. Insert height typically in the Bosch install window (often ~24–40 in / follow the sheet). Hose shoved to the trap is a siphon and a false E18.
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Pump impeller and non-return — Power off. Impeller free? Flapper/ball in the pump housing seating?
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Pressure chamber — Trace the thin hose from the air trap on the tub to the analog pressure sensor (on the control or a remote APS). Disconnect at the sensor: wet inside = flooded trap. Clear the chamber, dry the hose, reseat with no sagging loops that trap water.
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Electrical — Pump ohms and 120 VAC on drain; then 5 VDC at the analog sensor. Module last.
Multimeter and safety checks
Power off, connectors isolated, unless the row says live.
| Test | Setup | Typical result | Fail |
|---|---|---|---|
| Line voltage | Receptacle | 108–132 VAC | Fix supply first |
| Drain pump winding | Isolated pump pins | 15–40 Ω (US 120 VAC Bosch pumps; use the tech sheet) | ∞ Ω → E23 / replace pump. ~0 Ω shorted |
| Pump to core | Pin to laminated housing | ∞ Ω | Shorted pump |
| Drain command | Live, Drain program, door locked | 120 VAC at pump | No voltage: lock/module. Voltage + no flow + free impeller: valve/hose |
| Analog sensor supply | Live, isolated measurement at APS | ~5 VDC Vcc to ground | No 5 V: harness or module |
| Pressure hose | Mechanical, unplugged | Dry air, no water spit | Wet = flooded chamber → false E18 |
| Impeller | Hand, filter open | Free, slight magnet cog | Locked: debris; do not keep hitting Drain |
Do not jumper the analog sensor to “empty” to finish a cycle on a flooded machine. Do not chemical-flush the air trap with drain cleaner.
Root cause vs repair
| Finding | Fault | Action |
|---|---|---|
| Filter packed, impeller locked | Mechanical pump | Clean; replace pump if blades damaged |
| 15–40 Ω, 120 VAC, no flow | Non-return / hose | Clear valve; re-route standpipe |
| ∞ Ω pump | E23 electrical | Replace pump; prove module output |
| Drum empty, hose wet | Pressure chamber | Flush air trap; replace cracked chamber; dry hose |
| 5 V missing at APS | Sensor/module | Harness, then analog sensor or control |
| Suds lock, E18 after detergent overdose | Foam in trap | Run a clean cycle; correct detergent dose |
A new pump on a flooded pressure hose returns E18 on the next drain.
FAQ
What does E18 mean on a Bosch front-load washer?
Drain timeout. Pump, hose, non-return, or a pressure chamber that still says “full.”
How do I tell a bad drain pump from a bad pressure chamber?
Water still in the drum and a dead/locked pump → pump. Drum empty or draining, hose wet, E18 stays → chamber/sensor.
What should the drain pump read?
About 15–40 Ω isolated. Open is E23. Voltage without flow is mechanical.
Can I blow into the pressure hose to test it?
Gently, unplugged, to see if the trap is liquid-locked. Do not force water into the analog sensor.
When to schedule professional service
Book service when E18 survives a clean filter and a dry pressure hose, when the pump is open, or when E23 is stored. Schedule a washer diagnostic →
FAQ · Family-owned Port St. Lucie
Frequently Asked Questions About Bosch Washer E18
What does E18 mean on a Bosch front-load washer?
Drain timeout. The control did not see the tub empty in the allowed window. That can be a jammed pump, a kinked hose, a stuck non-return valve, or a flooded pressure chamber that still reports 'full' after the water is gone. It is not the same as dishwasher E15 AquaStop.
How do I tell a bad drain pump from a bad pressure chamber?
If the drum still holds water, the pump is silent or locked, and windings are open, it is the pump (or E23). If the drum is empty or clearly draining but E18 remains, pull the pressure hose off the analog sensor: a wet hose or gurgling chamber means the air trap is flooded and the board never sees empty.
What should the drain pump read on a meter?
Unplug, isolate the pump connector. Many US Bosch 120 VAC drain pumps read about 15–40 Ω. ∞ Ω is E23 territory. 120 VAC at the pump during drain with a free impeller and no flow is mechanical (filter, valve, hose), not a new module.
Can I blow into the pressure hose to test it?
Gently, with the machine unplugged, to confirm the air trap is not liquid-locked. Do not force water into the analog sensor port. If the hose spits suds, flush the chamber from the tub side and replace a cracked trap.