Error code reference

Bosch Dishwasher Error Code 1

Control module has timed out due to an unidentified heating problem; all heating related parts must be…

Bosch codesBosch dishwasher codes

Control module has timed out due to an unidentified heating problem; all heating related parts must be checked (displayed on module, not test program).

First step from the service manual

Check heater (~11 ohms), Hi-Limit (~0.3 ohms), flow switch (~0.4 ohms), NTC (~55k ohms at 72°F), circulation pump (~10 ohms), control module heater relay, and wire harness. Fix heating problem then run dishwasher to reset module.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

MyPros+ Max

Get the full diagnostic procedure for 1.

  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
  • Verified part numbers when replacement is required
Get the full procedure

$29/month · Cancel anytime · Or $9.95 3-day pass

What 1 means on a Bosch dishwasher

Error code 1 on a Bosch dishwasher indicates a fault with the Aqua Sensor, also sold under the Sensotronic name. The control board monitors the signal from this optical sensor continuously during the wash cycle. When the sensor returns an out-of-range signal, fails to respond, or produces an implausible reading, the board logs code 1 and may halt the cycle to prevent incorrect wash behavior. The fault can stem from a failed sensor, a break or short in the wiring harness connecting the sensor to the control board, or contamination on the sensor lens that blocks its optical path.

The Aqua Sensor is an optical device mounted in the sump area that measures how cloudy or dirty the wash water is. Bosch dishwashers use this data to automatically adjust water usage and cycle length, which is the core of the Sensotronic system. When the sensor malfunctions, the dishwasher cannot accurately judge water clarity and may default to a fault state rather than risk running an ineffective or wasteful cycle.

In many cases, heavy grease buildup or limescale on the sensor lens causes the optical reading to drift outside acceptable limits. Cleaning the sensor is a reasonable first step before replacing any parts. If cleaning does not resolve the fault, the sensor itself or its wiring harness will need to be tested and likely replaced.

Source: manufacturer service documentation.

Common causes of 1

  1. 01

    Contaminated Aqua Sensor lens

    Wiring / connection

    Grease, food residue, or limescale deposits on the optical lens of the Aqua Sensor block or scatter the light beam, producing readings the control board rejects as invalid. Cleaning the lens with a soft cloth and a mild descaling solution can resolve this without any parts replacement.

  2. 02

    Failed Aqua Sensor (Sensotronic unit)

    Part replacement

    The optical sensor itself can fail internally due to age, moisture ingress, or electrical surge, causing it to output a constant incorrect signal or no signal at all. A failed sensor must be replaced to clear the fault.

  3. 03

    Damaged or corroded wiring harness to the Aqua Sensor

    Part replacement

    The wiring harness connecting the Aqua Sensor to the main control board can develop breaks, corrosion at the connector pins, or shorts from heat and moisture exposure. This interrupts the signal path and triggers the fault even when the sensor itself is functional.

  4. 04

    Faulty main control board

    Part replacement

    If the sensor and its wiring both test within spec, the control board's sensor input circuit may have failed and is misreading or ignoring the sensor signal. This is the least common cause and should only be suspected after the sensor and wiring have been ruled out.

See the test procedure for each cause

Frequently asked questions about 1

What does error code 1 mean on a Bosch dishwasher?
Error code 1 on a Bosch dishwasher signals a fault with the Aqua Sensor, also called the Sensotronic sensor. This optical sensor measures water clarity in the sump to help the dishwasher automatically adjust wash intensity and water use. When the control board detects an invalid or missing signal from this sensor, it triggers code 1 and may stop the cycle.
How do I fix error code 1 on a Bosch dishwasher?
Start by locating the Aqua Sensor in the sump area at the bottom of the dishwasher and cleaning its optical lens with a soft cloth and a mild descaler or white vinegar to remove grease and limescale buildup. If the code returns after cleaning, use a multimeter to check the sensor wiring harness for continuity and inspect the connector pins for corrosion. If the wiring is intact and the fault persists, the Aqua Sensor unit itself needs to be replaced, which is a moderate DIY repair requiring removal of the lower spray arm and sump cover.
Can I still use my Bosch dishwasher when error code 1 is showing?
Running the dishwasher with code 1 active is not recommended. Without a functioning Aqua Sensor, the control board cannot regulate wash cycles based on water clarity, which can result in poor cleaning performance, excessive water use, or an incomplete cycle. On some Bosch models the dishwasher will halt mid-cycle when this fault is detected, making continued use impractical until the sensor issue is resolved.
How much does it cost to fix error code 1 on a Bosch dishwasher?
If cleaning the sensor lens resolves the fault, there is no parts cost. A replacement Bosch Aqua Sensor unit typically costs between $20 and $60 depending on the specific model. If you hire a technician, expect an additional $80 to $150 in labor, bringing the total repair to roughly $100 to $210. The sensor replacement itself is accessible to confident DIYers with basic tools, which keeps costs lower if you do the work yourself.
Will resetting my Bosch dishwasher clear error code 1?
A reset may temporarily clear the code, but it will return as soon as the control board polls the Aqua Sensor again during the next cycle. To clear code 1 permanently, the underlying sensor fault must be corrected by cleaning the sensor lens, repairing the wiring, or replacing the sensor. A reset alone is not a fix for this code.

Related Bosch dishwasher codes

All Bosch dishwasher codes
View all 240 Bosch dishwasher codes

78,000+ service manuals · 160,000+ error codes · 55+ brands

Get Started

$29/month · Cancel anytime · Or $9.95 3-day pass