What does P0602 mean?
The control module detected a programming or calibration error.
Quick Decision Guide
- Low battery voltage
- Poor module ground
- Corroded PCM connector
When to stop driving
Do not rely on the vehicle if it stalls, fails to start, loses communication with modules, or shows multiple control-module faults.
Reviewed by ratchit Automotive Solutions for clarity and inspection-first safety framing. Not a substitute for professional diagnosis.
Repair Decision & Cost Guide
Use this guide to decide what to inspect first, what it may cost, and when to move from DIY checks to professional diagnosis.
P0602 is a clue, not a confirmed diagnosis. Inspect simple causes before replacing parts.
DIY vs. Shop
Can you keep driving?
Best first DIY check
Don't replace this first
When to seek a shop
Recommended next action
Estimated Repair Cost
Inspection cost
Free OBD2 read at most parts stores
DIY parts cost
$0–$900
Inspect first before replacing parts.
If the vehicle is unsafe to drive, stop driving and seek professional help.
Shop diagnostic cost
$80–$150 (typical shop diagnostic fee)
Shop repair cost
$100–$1,800
Diagnostic uncertainty: This code points to a system or condition, not a guaranteed failed part. Inspect before replacing.
Cost variation: Costs vary by vehicle, location, part quality, labor rate, and the confirmed root cause.
Inspect Before Replacing
These checks are cheap, fast, and rule out the most common causes before spending money on parts.
- 1Check battery condition and charging voltage before replacing any module.
- 2Scan for U-codes, voltage codes, and companion module communication faults.
Save this issue to My Garage
Save this issue to My Garage, track what you inspect, and build service history for this vehicle.
V-IQ readiness preview: High impact — resolving and tracking this issue may noticeably improve your V-IQ readiness. Tracking active codes and resolutions builds a service history we use to estimate V-IQ readiness over time.
Understanding P0602 in detail
P0602 is a control-module related diagnostic trouble code. It can indicate internal memory faults, programming problems, communication faults, or a module that is not retaining learned data correctly. These codes should not trigger immediate module replacement. Low battery voltage, poor grounds, water intrusion, aftermarket tuning, failed programming, or connector corrosion can mimic a failed PCM/ECM. Diagnosis should start with battery and charging voltage, module powers and grounds, scan-tool communication, connector inspection, and technical service bulletin checks before condemning the control module.
Symptoms of P0602
- Check engine light
- No-start or hard start
- Poor drivability
- Multiple unrelated codes
- Communication faults
- Readiness monitors may not complete
Common causes
- Low battery voltage
- Poor module ground
- Corroded PCM connector
- Interrupted programming
- Internal PCM memory fault
- Aftermarket tuning or calibration issue
How to diagnose P0602
Steps ordered by urgency — tackle Now items first.
- NowCheck battery condition and charging voltage before replacing any module.
- NowScan for U-codes, voltage codes, and companion module communication faults.
- SoonInspect PCM/ECM connectors for water intrusion, corrosion, or loose pins.
- SoonVerify module powers and grounds with a wiring diagram.
- LaterCheck for software updates, calibration issues, and TSBs before module replacement.
How to fix P0602
Fixes listed in order of likelihood and cost-efficiency.
- 1Repair battery or charging issue
- 2Repair module power/ground
- 3Repair connector corrosion
- 4Reprogram PCM/ECM
- 5Replace PCM/ECM only after testing confirms failure
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Estimated Repair Cost — P0602
Ranges vary by vehicle, region, and shop. Use as a ballpark — always get a quote.
DIY estimate
$10 – $180
Shop estimate
$100 – $400
DIY estimate
$0 – $50
Shop estimate
$150 – $600
DIY estimate
$250 – $900
Shop estimate
$700 – $1,800
Cost data is estimated and may not reflect your specific vehicle or location.
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Frequently Asked Questions
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