Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1998 GMC EnvoyFACTORY OEM SERVICE PROCEDURE
TBC Module DTC Definitions
TBC MODULE DTC DEFINITIONS
| DTC | Circuit Affected | ||
|---|---|---|---|
| B1397 | 5-Volt Reference Circuit Low | ||
| B1398 | 5-Volt Reference Circuit High | ||
| B1477 | RAP Circuit Low | ||
| B1478 | RAP Circuit High | ||
| B1480 | Inadvertent Power Circuit Malfunction | ||
| B2527 | Front Foglight Circuit Low | ||
| B2537 | Rear Foglight Circuit Low (Export Only) | ||
| B2575 | Headlight Request/Feedback Mismatch | ||
| B2577 | Headlight Control Circuit Low | ||
| B2585 | Park Light Control Circuit Malfunction | ||
| B2600 | Daytime Running Light Circuit Malfunction | ||
| B2613 | Dimming Potentiometer Circuit High | ||
| B2617 | Courtesy Light Circuit Low | ||
| B2618 | Courtesy Light Circuit High | ||
| B2647 | Ambient Light Sensor Circuit Low | ||
| B2648 | Ambient Light Sensor Circuit High | ||
| B2752 | Horn Relay Coil Circuit Low | ||
| B2947 (1) | Security System Sensor Power Circuit Low | ||
| B2948 (1) | Security System Sensor Power Circuit High | ||
| B2957 (1) | Security System Sensor Circuit Low | ||
| B2958 (1) | Security System Sensor Circuit High | ||
| B2960 (1) | Security System Sensor Data Incorrect But Valid | ||
| B2961 | Ignition 1 - Key In/Out Mismatch | ||
| B3031 (1) | Security System Controller In Learn Mode | ||
| B3033 (1) | Security System Indicates Tamper | ||
| B3102 | Keyless Entry (RFA) Data Link Circuit Low | ||
| B3137 | Door Lock Circuit Low | ||
| B3138 | Door Lock Circuit High | ||
| B3147 | Passenger Door Unlock Circuit Low | ||
| B3148 | Passenger Door Unlock Circuit High | ||
| U1255 | Class 2 Communication Malfunction | ||
| U1301 | Class 2 Data Link High | ||
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Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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