Fix P0602: Mechanic’s solutions that WORKED

The OBD2 code P0602 signals a “Control Module Programming Error,” indicating that the vehicle’s engine control module (ECM) or transmission control module (TCM) has encountered issues with its software or programming.

This can manifest in various driveability issues, including erratic shifting, stalling, or even the vehicle’s failure to start. Such a problem can arise from incorrect module programming, software corruption, or a failure to update to the manufacturer’s latest software version. It’s a critical signal that the vehicle’s “brain” isn’t functioning as expected, requiring immediate attention to avoid further complications.

P0602 quick overview

Meaning	P0602: Control Module Programming Error
Is it serious?	Yes, this error can affect the vehicle’s performance and reliability significantly.
Possible causes	Incorrect programming of the ECM/TCM Software corruption within the control module Faulty ECM/TCM Disconnection or interruption of battery power
How to diagnose?	Check for TSBs and manufacturer recalls related to ECM/TCM programming. Perform a quick learn procedure on the control module to see if it resolves the issue. Inspect wiring and connectors for damage or corrosion that may affect communication. Verify battery connections and health to rule out power issues causing the code. Consider ECM/TCM replacement if reprogramming and quick learn do not resolve the issue.

How to fix P0602 – learn from mechanics

I looked into P0602 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Chrysler

Vehicle information 2005 Chrysler Town & Country Limited 3.3L

Issue + repair history

• OBD2 code P0602 (Control Module Programming Error) detected.
• Symptoms include harsh downshift from 3-2, accompanied by a jolting feeling when slowing down from over 40 mph.
• Previous trans codes resolved with bad connections at the solenoid valve.

Other OBD2 Codes + Test Results

• OBD2 Codes: P0602 (Control Module Programming Error), P1684 (Battery Disconnected within Last 50 Starts).

Mechanic suggestions

• Check for technical service bulletins (TSB) for potential reflash procedures issued by the manufacturer.
• Consider replacing the control module if the code persists after clearing and performing a quick learn procedure.
• Verify if there was a battery disconnection recently, as it could explain the P1684 code.
• Inspect cvi values and seals for potential leaks causing the harsh downshift from 3-2.

Final fix

• Performing a quick learn procedure resolved the issue, indicating that a control module replacement may not be necessary at this time.

Case #2: Jeep

Vehicle information 2015 Jeep Compass Sport 2.0L

Issue + repair history

• Dash gauges jumping, lights flashing, vehicle bucking when accelerating from cruising at 70 mph
• Communication with TCM lost
• Replaced TCM due to communication issue and U10A code
• New TCM sets code P0602 program failure
• Unable to clear codes after replacing TCM
• “Software Idle Switch Signal” never changes to “On” with key power in new TCM

Other OBD2 Codes + Test Results

• B+ pin 4 C2: 13.5V
• Ground: 0.0 ohms
• CAN C+ volts: 2.5V
• CAN C- volts: 2.5V
• Trans Control O/P volts pin 10 and 19 C1: 13.5V
• Software Idle Switch Signal: Off

Mechanic suggestions

• Check wiring for any issues elsewhere
• Ensure that the eprom in the transmission is programmed to the TCM
• Use diagnostic tools like Snap-on Zeus for TCM initialization

Final fix

• Took new TCM and vehicle to dealer for flashing SIM codes into the TCM
• Found and repaired chafed wire on the CAN C Buss wire at the I201A connector in the driver’s front fender, then secured the connector

Case #3: Chevrolet

Vehicle information 2006 Chevrolet Impala LT 3.5L

Issue + repair history

• Vehicle stalls after being driven for at least 30 minutes
• Sets code P0602
• Reflashed ECM and TCM, replaced TCM due to U10A code, still same problem
• Additional codes: P0842 (trans temp) and P0717 (input speed sensor cir low voltage)

Other OBD2 Codes + Test Results

• P0601: Control module read-only memory
• P0842: Transmission temperature
• P0717: Input speed sensor circuit low voltage
• Test results:
  • B+ pin 4 C2: 13.5V
  • Ground: 0.0 ohms
  • CAN C+ volts: 2.5V
  • CAN C- volts: 2.5V
  • Trans Control O/P volts pin 10 and 19 C1: 13.5V
  • Software Idle Switch Signal: Off

Mechanic suggestions

• Replace ECM as well as TCM
• Confirm power and ground, replace ECM if okay
• Try with another ECM if problem persists after TCM replacement
• Check wiring and test fuel pump for possible related issues

Final fix

• Replaced ECM and programmed it, along with TCM
• Vehicle on road test after ECM replacement

Diagnostic Step	Brief Explanation
Consult TSBs and recalls	Manufacturers may provide specific guidance or updates for known programming issues.
Perform quick learn procedure	Resets the control module to relearn its adaptive settings, potentially fixing programming errors.
Inspect electrical connections	Ensure that the battery, wiring, and connectors are in good condition to support proper module function.
Reprogram or replace ECM/TCM	If issues persist, reprogramming or replacing the faulty module may be necessary, often requiring dealer support.
Verify repair with a test drive	After repairs, a thorough test drive can confirm the resolution of the original symptoms and code clearance.

These steps, synthesized from real-world mechanic experiences, highlight the technical nature of resolving a P0602 code. A methodical approach, from simple resets and inspections to potentially complex module replacement, ensures the vehicle is restored to its optimal state.