Code
P0428
ISUZU
P — Powertrain
Catalyst Temperature Sensor Circuit High Sensor 1
Views:
UK: 23
EN: 66
RU: 37
AI status
Completed
Completed
100%
Causes
- Open, short or damaged wiring in catalyst temperature sensor circuit
- Corroded, loose, or contaminated sensor connector
- Failed catalyst temperature sensor (NTC/thermistor or integrated sensor)
- Internal PCM/input circuit fault
- Excessive exhaust temperature or damaged catalytic converter causing out-of-range reading
- Aftermarket exhaust/component modification altering sensor environment
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated (Check Engine Light)
- Failed emissions test or readiness monitors not setting
- Possible fuel trim or engine protection strategies (reduced power) if PCM limits operations
- Unusual exhaust heat or odor if catalyst is damaged
- No obvious drivability symptom in some cases
What to check
- Retrieve freeze-frame and live data with a scan tool (catalyst temp sensor voltage/temperature, related O2 and catalyst monitors)
- Check trouble codes in addition to P0428 (look for heater, O2, or catalyst efficiency codes)
- Visually inspect sensor, connector and wiring for damage, heat exposure, corrosion or contamination
- Backprobe sensor connector and confirm reference voltage/ground where applicable with key ON, engine OFF
- Measure sensor resistance and/or voltage vs. temperature and compare to specification
- Inspect catalytic converter for external heat damage, discoloration, or rattling (indicative of internal damage)
Signal parameters
- Typical sensor signal: 0.1–5.0 V (depends on sensor type); voltage will change with exhaust temperature (higher temp → higher/lower voltage depending on sensor)
- Some sensors are NTC thermistors — resistance decreases as temperature rises (specs vary by sensor)
- Heater circuit (if equipped): specific coil resistance value and current draw — should not be open or shorted
- PCM input circuit expects stable signal without rapid spikes or stuck high voltage
Diagnostic algorithm
- Connect a capable scan tool, record freeze frame and live data for catalyst temp (Bank 1 Sensor 1), upstream O2 and downstream O2 if available. Note when code sets.
- Visually inspect sensor, connector and wiring harness for heat damage, chafing, corrosion, pin push-out or contamination. Repair or replace damaged harness/connector as needed.
- With ignition OFF, disconnect sensor and inspect pins. Check sensor harness continuity to PCM and to ground/12V where applicable. Repair shorts/opens.
- Measure sensor resistance at ambient and compare to manufacturer spec (or heat sensor slowly and observe resistance change). If sensor is out of spec or does not change with temperature, replace sensor.
- With sensor connected and engine running or using heat source (follow safety precautions), backprobe sensor signal and compare voltage/temperature behavior to spec. Reproduce high reading or intermittent behavior by wiggle testing harness.
- Inspect catalytic converter condition visually and by temperature measurement (use IR thermometer to compare upstream vs downstream temps). Excessive downstream temps or strange delta may indicate damaged converter producing abnormal heat.
- If wiring and sensor check good, check PCM input and grounds. Perform voltage and ground integrity checks at PCM connector. Replace PCM only after ruling out external causes and verifying correct signal behavior.
- Clear codes and test drive to confirm fault does not return. If code returns, complete repairs as indicated (sensor replacement, harness repair, converter replacement).
Likely causes
- Broken or chafed sensor harness near exhaust or frame (open to voltage or short to battery voltage)
- Connector pins pushed out or corroded at the sensor or PCM
- Moisture intrusion or soot in connector causing high reading
- Sensor element failed open or reporting much higher resistance/voltage than spec
- Catalyst internally failing or glowing, producing abnormally high exhaust temperatures
Fault status
Status
PCM reports catalyst temperature sensor circuit HIGH for Bank 1 Sensor 1 — sensor signal is above expected range or showing abnormally high temperature/voltage.
Repair difficulty: Medium
Diagnostic time: 1.0 - 3.0 hours
Similar codes
Repair manuals
Manual library for ISUZU
43
Browse 43 ISUZU manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
ISUZU
-
ISUZU: 2008
-
ISUZU: 2007
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email