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.
1990 Chevrolet Caprice Base, 4.3 Z, 4L60/MD8FACTORY OEM SERVICE PROCEDURE
Code 13, Open Oxygen Sensor Circuit
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- This tests if problem still exists. Code 13 indicates an open in the O2 sensor circuit under the following conditions:
- Coolant temperature at least 108°F (42°C).
- Neither Code 21 nor Code 22 are stored.
- O2 sensor voltage is within a specified range (.34-.55 volt).
- Throttle angle is greater than 6 percent (off-idle).
- More than 40 seconds have elapsed since start-up.
- All conditions have existed for at least 20 seconds.
- Determines if O2 sensor, wiring or ECM is at fault.
- This tests O2 sensor circuit wiring. Use only a high impedance (10-megohm minimum) digital voltmeter.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
Comes to youSame-day available12-month warranty
Get a Free QuoteNo obligation. See pricing before you book.