Code
P1483
PONTIAC
P — Powertrain
Catalyst Temperature Sensor Circuit Shorted High
Views:
UK: 16
EN: 38
RU: 25
AI status
Completed
Completed
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Causes
- Short to battery voltage (5V reference or other supply) in sensor harness
- Open or shorted sensor element (thermistor) inside the catalyst temperature sensor
- Corroded, damaged, or disconnected connector or wiring (harness insulation chafing)
- Poor or missing ground at sensor/PCM
- PCM input or internal driver fault
- Aftermarket exhaust work or sensor installed incorrectly (wrong sensor type/connector)
Symptoms
- Check Engine Light (MIL) on
- Possible reduced engine performance or limp mode depending on vehicle strategy
- Failed emissions test or catalyst efficiency-related symptoms
- Stored freeze-frame data or related emissions codes (O2/catalyst codes)
What to check
- Read and record all stored codes and freeze-frame data with a scan tool
- Visual inspection of catalyst temperature sensor, connector, and wiring for damage, heat exposure, or corrosion
- Backprobe sensor connector and monitor voltage with key ON / engine OFF and with engine running if safe
- Check for continuity to PCM and for short to battery voltage or to ground
- Measure sensor resistance with sensor disconnected (compare to spec if available)
- Wiggle harness while monitoring live data to check for intermittent faults
Signal parameters
- Typical thermistor-type catalyst temp sensor voltage: ~0.2–4.8 V (varies by design) — cold = high voltage, hot = low voltage with pull-up configuration
- Shorted-high condition: sensor circuit voltage near supply (≈ 4.5–5.0 V) or no change with temperature
- Expected behavior: voltage should change smoothly as exhaust/catalyst temperature changes during warm-up
- Resistance (typical thermistor) at ambient: often in the kilo-ohm range (manufacturer-specific) — confirm with service manual
Diagnostic algorithm
- Retrieve freeze frame and all related codes. Note conditions when the code set (temp, load, RPM).
- Perform a careful visual inspection of the catalyst temp sensor, its connector, and wiring to the PCM. Look for heat damage, chafing, pin corrosion, splices, or melted insulation.
- With ignition ON (engine OFF), backprobe the sensor connector and measure reference voltage and sensor signal voltage. Compare to typical values: a short-high will show signal near battery/reference voltage.
- With engine cold then warmed (if safe), monitor live sensor voltage while warming up the exhaust. Confirm voltage changes with temperature. If no change and voltage high, suspect short or open sensor.
- Disconnect the sensor and measure resistance across sensor terminals. Compare to manufacturer spec. An open or out-of-spec high resistance indicates sensor failure.
- Check for short to 5V or battery: with harness connected, measure voltage between sensor signal wire and battery positive/other circuits; inspect for unintended continuity. With harness disconnected, check for continuity between signal wire and 5V feed or other circuits.
- Check connector pin voltages at PCM and for continuity/shorts between signal, reference, and ground pins (repair wiring as needed).
- If wiring and sensor check good, test or substitute a known-good sensor (if available) or inspect PCM connector for bent pins. Replace sensor or repair harness as required.
- After repair, clear codes and perform a drive cycle to verify the code does not return and that sensor values behave normally.
- If fault persists after verifying wiring and sensor, consider PCM diagnosis/repair by a qualified technician.
Likely causes
- Damaged wiring harness where it passes near the exhaust/catalyst
- Connector pins pushed out, corroded, or contaminated
- Failed catalyst temperature sensor (open or internal short)
- Short to key-on battery voltage due to pin contact or spliced feed
- PCM terminal fault (less common)
Fault status
Status
Catalyst Temperature Sensor Circuit Shorted High — sensor circuit reporting excessive/high voltage
Repair difficulty: Medium
Diagnostic time: 0.8-2.0 hours
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