Diagnostic trouble code P1587 is a manufacturer-specific powertrain fault code. Because it is manufacturer-specific, its exact definition depends entirely on the vehicle make, model, and application.
Exact vehicle application must be verified before diagnosis. The code identifies a detected condition in a specific subsystem, but further testing is required to identify the root cause.
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Key Takeaways
- P1587 is a manufacturer-specific code, meaning its definition varies significantly between automakers like Nissan, General Motors, and Toyota.
- Possible causes depend on the vehicle and may include ECM/TCM communication faults, torque request signal issues, or cruise control circuit malfunctions.
- Symptoms vary by application but can include an illuminated Check Engine Light, erratic shifting, or disabled cruise control.
- Diagnosis requires verifying the exact factory definition for the specific vehicle and following the manufacturer’s targeted testing procedures.
- Repairs depend on the confirmed root cause and may involve repairing wiring, updating software, or replacing specific control modules.
P1587 Code Description and Implications
Because P1587 is manufacturer-specific, there is no single universal definition. The exact monitored system and fault condition depend on the vehicle make and model.
Some Nissan and Infiniti applications: P1587 typically indicates an “MT/AT Recognition Error.” The Engine Control Module (ECM) and Transmission Control Module (TCM) fail to properly communicate or agree on the installed transmission type.
Certain General Motors (GM) applications: P1587 often designates a “Transmission Control Module (TCM) Engine Torque Request Signal Circuit” fault, where the TCM detects an implausible signal from the ECM regarding engine torque output.
Specific Toyota and Lexus applications: P1587 can indicate a “Cruise Control System” or “Stop Light Switch” circuit malfunction, preventing the cruise control system from engaging safely.
Common Causes of the P1587 Code
The underlying cause depends entirely on the verified factory definition for the specific vehicle application.
For applications monitoring MT/AT recognition, possible causes include software mismatches between the ECM and TCM, damaged CAN bus wiring, or a failed control module.
For applications monitoring the torque request signal, causes often involve an open or short in the discrete signal circuit between the ECM and TCM, or poor electrical grounds.
For applications monitoring the cruise control or stop light switch, causes may include a misadjusted brake pedal switch, damaged wiring to the steering wheel controls, or a failed cruise control actuator.
Symptoms Associated With P1587
Symptoms vary widely depending on the underlying system fault and the vehicle manufacturer.
On applications with an MT/AT recognition fault, the primary symptom is an illuminated Check Engine Light, often accompanied by erratic shifting, harsh gear engagements, or the transmission entering a fail-safe mode.
On applications with a torque request signal fault, the vehicle may experience reduced engine power, harsh transmission shifts, or disabled traction control systems.
On applications with a cruise control fault, the cruise control system will simply refuse to engage, and a warning light may illuminate on the dashboard.
Diagnosing the P1587 Trouble Code
Diagnosis must begin by confirming the exact factory definition for the specific make, model, and year. Attempting to diagnose a cruise control switch on a vehicle where P1587 indicates a transmission recognition error will lead to misdiagnosis.
For MT/AT recognition applications, technicians typically verify the ECM and TCM software calibration levels and inspect the CAN communication network for wiring damage or corrosion.
For torque request signal applications, diagnosis involves checking the discrete signal circuit between the ECM and TCM for continuity, shorts to ground, or shorts to voltage.
Repairing the P1587 Issue
Repairs must follow confirmed diagnosis based on the specific vehicle application.
If testing confirms a software mismatch or communication fault between the ECM and TCM, reprogramming the modules or repairing the CAN bus wiring may be required.
If a torque request signal circuit fault is confirmed, the damaged wires or connectors must be repaired to restore proper signal transmission.
If a cruise control or stop light switch fault is confirmed, adjusting the brake pedal switch or replacing the faulty switch assembly may resolve the issue.
Cost Considerations for P1587 Repairs
Repair costs depend entirely on the confirmed root cause, component accessibility, and local labor rates.
Repairing a damaged wire or adjusting a brake light switch may require minimal parts and labor. Conversely, replacing and programming an ECM or TCM requires significant diagnostic time, specialized equipment, and expensive components.
Prevention Strategies for Future Occurrences
Some electrical or software failures cannot be reliably prevented. However, ensuring that aftermarket electrical accessories are properly installed and do not interfere with the vehicle’s CAN bus network can help prevent communication faults.
Keeping the battery and charging system in good condition helps prevent voltage spikes that can corrupt control module software or damage sensitive communication circuits.
Troubleshooting Tips and Best Practices
Never assume P1587 is a universal transmission or cruise control code. Always verify the exact definition for the specific vehicle before purchasing parts or beginning electrical testing.
Do not ignore related codes. A communication fault frequently appears alongside network-specific U-codes, while a stop light switch fault may trigger additional brake system or cruise control warnings.
Check for technical service bulletins applicable to your exact vehicle application, as manufacturers frequently release updated software calibrations to resolve known ECM/TCM communication mismatches.
More OBD-II Codes
| P1555 | P1588 | P0700 | P0111 |
| P1565 | P1600 | U0101 | P0130 |
| P1571 | P1602 | P1714 | P0136 |
| P1574 | P1604 | P1716 | P0141 |
| P1580 | P1605 | P1718 | P0150 |
| P1586 | P1606 | P1720 | P0155 |
Frequently Asked Questions
Is P1587 a generic or manufacturer-specific code?
No. P1587 is a manufacturer-specific code. Its exact definition varies significantly between automakers, so the factory service information for the specific vehicle must be consulted.
Can I drive my car with a P1587 code?
It depends on the application. If P1587 indicates a transmission recognition or torque request fault, driving could cause harsh shifts or transmission damage. If it indicates a cruise control fault, the vehicle is usually safe to drive.
Will disconnecting the battery clear the P1587 code?
Disconnecting the battery may temporarily clear the code, but it does not repair the underlying electrical or software fault. The code will return once the module runs its self-test.
Can a bad battery cause a P1587 code?
On applications relying on sensitive CAN bus communication or module software, low system voltage or voltage spikes from a failing battery can disrupt module communication and trigger network-related faults.
Does P1587 always mean the transmission control module is bad?
No. While a failing module can cause communication faults, damaged wiring, poor grounds, software mismatches, or faulty external switches are frequent causes that must be ruled out first.
What Should You Do About the P1587 Code?
Confirm the exact factory definition and diagnostic procedure for your specific vehicle application. Because P1587 is manufacturer-specific, identifying whether it relates to transmission recognition, torque request signals, or cruise control systems is the mandatory first step.
Follow the applicable manufacturer diagnostic steps to test the relevant system and components. Once the root cause is confirmed, complete the necessary repairs and verify that the system operates correctly and the code does not return.
