Chevrolet Avalanche B1566 Engine Trouble Code
What is Chevrolet Avalanche B1566?
Chevrolet Avalanche B1566 indicates potential catalytic converter failure. If completely failed, your vehicle may not run properly and fuel economy will suffer significantly. Average replacement cost is $2,000–$2,140. This repair requires professional service and should not be delayed.
B1566 on the Chevrolet Avalanche
On the Chevrolet Avalanche, a secondary air injection pump that has seized due to moisture ingress is a common trigger for B1566. The fault is usually only present on cold starts and clears itself after two to three warm-up cycles, making it easy to overlook.
Code Information
| Code Type: | OBD-II Body (B) Trouble Code |
| System: | Body |
| Vehicle: | Chevrolet Avalanche |
| Brand: | Chevrolet |
| Model: | Avalanche |
| Code: | B1566 |
B1566 Chevrolet Avalanche Symptoms
Check Engine Light
Illuminated Chevrolet Avalanche dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Chevrolet Avalanche
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Chevrolet Avalanche
Increased Emissions
Failed emissions test due to B1566
B1566 Code Structure
Understanding what each digit means in the B1566 body trouble code:
| B | 1 | 5 | 6 | 6 |
|---|---|---|---|---|
| Body Code | Fuel And Air Metering | Fuel Composition Sensor Circuit Malfunction | Cylinder 4 Contribution/Balance Fault | Ignition Coil A Primary/Secondary Circuit Malfunction |
How to Fix Chevrolet Avalanche B1566
Diagnostic Steps:
The catalytic converter has oxygen sensors before and after it. When warm and in closed-loop mode, the upstream O2 sensor reading should fluctuate, while downstream should remain steady.
Repair Solution:
Firing order is engineered to minimise vibration. Altering firing order results in mistimed ignition and poor engine operation. Consult vehicle-specific repair manual for correct firing order.
Technical Notes:
B1566 on electronically controlled automatic transmissions relates to shift solenoid operation. The solenoid actuates hydraulic circuits controlling clutches or bands for gear changes.
Chevrolet Avalanche B1566 Repair Cost
For Chevrolet Avalanche diesel variants with swirl flap actuator failure causing B1566, the repair ranges from $180 (actuator only) to $900+ if a broken flap has been ingested by the engine. Early intervention is strongly recommended.
B1566 Description
B1566 engine trouble code is related to Ignition Coil A Primary/Secondary Circuit Malfunction.
Main Cause
The primary reason for B1566 OBD-II Engine Trouble Code is: Fuel Composition Sensor Circuit Malfunction.
Common B1566 Misdiagnosis on the Chevrolet Avalanche
The Chevrolet Avalanche is frequently taken to workshops for a B1566 fault where the technician replaces the throttle position sensor (TPS). In a significant proportion of cases, the root cause is a loose or cracked vacuum hose downstream of the throttle body that should have been found in a basic visual inspection.
DIY Repair Guide: B1566 on Chevrolet Avalanche
The throttle body on the Chevrolet Avalanche can be cleaned without full removal. Use a clean rag and throttle body cleaner spray with the engine off and cool. After cleaning, an idle relearn is mandatory: disconnect the battery for 10 minutes, reconnect, and allow the engine to idle for 10 minutes undisturbed.
Preventing B1566 on the Chevrolet Avalanche
Ensure the Chevrolet Avalanche oil cap and dipstick tube seal are airtight. Even a small crank-case vacuum leak can cause the PCM to log B1566 and, over time, allows moisture-laden air to degrade the engine oil faster than the scheduled service interval.
Frequently Asked Questions — Chevrolet Avalanche B1566
A: Temporarily clearing B1566 can help determine whether it is intermittent or persistent, but it does not fix the underlying fault. The code will return if the problem is still present. Do not clear codes just before an emissions test without a proper drive cycle.