What Does P1193 Mean?
The downstream oxygen sensor heater circuit has an open condition preventing heater operation. This is functionally similar to P1191, indicating no current flow through the heater element.
Common Causes
40%
Failed oxygen sensor with broken internal heater element
30%
Broken wire or poor connection in heater power or ground circuit
15%
Blown oxygen sensor heater fuse
10%
Failed heater relay or ECU heater driver circuit
5%
Corroded connector terminals creating high resistance/open circuit
Diagnostic Steps
1
Step 1: Verify oxygen sensor heater fuse condition and replace if blown
2
Step 2: Disconnect oxygen sensor and measure heater resistance at sensor (should be 3-30 ohms typically)
3
Step 3: Check for power supply voltage at heater circuit with key on, engine running
4
Step 4: Test ground circuit continuity from sensor connector to ECU or chassis ground
5
Step 5: If power, ground, and wiring are intact but sensor shows open circuit, replace oxygen sensor
Estimated Repair Cost
$100 - $400
Parts + labor, varies by vehicle and location
The downstream oxygen sensor heater circuit has an open condition preventing heater operation. This is functionally similar to P1191, indicating no current flow through the heater element.
The most common cause of P1193 (Oxygen Sensor Heater Circuit Open Downstream) is: Failed oxygen sensor with broken internal heater element
Typical repair costs for P1193 range from $100 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive but catalyst efficiency monitoring will not function properly, potentially allowing emissions problems to go undetected.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1193 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control
Difficulty
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