tracing error code 13 [no o2 sensor readings]
Thread Starter
8th Gear
Joined: Jan 2021
Posts: 8
Likes: 0
From: Illinois
tracing error code 13 [no o2 sensor readings]
I'm getting error code 13 on my 1989 L98 Corvette. My first change was to replace the 02 sensor, but the error persists.
Today, I disconnected the o2 sensor connector and instead hooked up my volt meter, using of the frame grounds for the 'other side'. All testing was with the car sitting in my driveway. I let the engine run for a while to get up to temp. While idling at around 600 to 700 RPM, the voltage reading bounced around a good bit (max values around 0.6 with some values near 0), but was generally around 0.1 V. When I held the rpm steady at anything greater than idle (1200 or 2000), the voltage dropped to around 0.001V and was very stable.
The engine sounds fine to my amateur ear, and the car drives just fine as well. I don't see or hear any exhaust leaks. Exhaust appears to exit from both sets of tail pipes pretty evenly.
Today's test suggests that my o2 sensor is okay. But I don't understand why the voltage would go to zero at higher rpms. That suggests no difference between the o2 levels inside and outside of the sensor!
Any suggestions for troubleshooting or further testing are welcome! Thanks
Today, I disconnected the o2 sensor connector and instead hooked up my volt meter, using of the frame grounds for the 'other side'. All testing was with the car sitting in my driveway. I let the engine run for a while to get up to temp. While idling at around 600 to 700 RPM, the voltage reading bounced around a good bit (max values around 0.6 with some values near 0), but was generally around 0.1 V. When I held the rpm steady at anything greater than idle (1200 or 2000), the voltage dropped to around 0.001V and was very stable.
The engine sounds fine to my amateur ear, and the car drives just fine as well. I don't see or hear any exhaust leaks. Exhaust appears to exit from both sets of tail pipes pretty evenly.
Today's test suggests that my o2 sensor is okay. But I don't understand why the voltage would go to zero at higher rpms. That suggests no difference between the o2 levels inside and outside of the sensor!
Any suggestions for troubleshooting or further testing are welcome! Thanks
Thread Starter
8th Gear
Joined: Jan 2021
Posts: 8
Likes: 0
From: Illinois
I'm not sure which side of the connector would be considered the male for the O2 sensor. For my test today, I inserted a butt-connector that is tied to my volt meter into the O2 sensor side of the connector. I don't think it likely that the interior pin would have been pushed back by that. Also, my old o2 sensor still has an exposed pin, which suggests it was not the original problem.
Thread Starter
8th Gear
Joined: Jan 2021
Posts: 8
Likes: 0
From: Illinois
I checked the wire from the o2 sensor connector to the ecm connector. It showed continuity. I also added a small bit of dielectric grease to the pins that connect to the ecm's o2 sensor places. No change.
In the service manual for the 'lean exhaust condition", I read that the ecm should supply a voltage of about 0.45V between the ecm's pins. The manual states: "The o2 sensor varies the voltage within a range of about 1 volt, if the exhaust is rich, down through about 0.1 volt if the exhaust is lean". Lean error is thrown for voltages less than 0.2; rich error when voltage is greater than 0.7.
Are those values the ecm voltage + sensor reading? Or just the sensor reading?
My sensor shows about 0.6 volts after releasing the throttle [which should be a fairly rich state]. Most of the time [idle to 2000 RPM while in park] my sensor is reporting 0.01 to 0.1 V. I would be surprised if the engine is running lean all the time. Maybe? Do those values seem reasonable?
I just picked up a remanufactured ecm. I'll give it a shot once I understand what I am looking for.
In the service manual for the 'lean exhaust condition", I read that the ecm should supply a voltage of about 0.45V between the ecm's pins. The manual states: "The o2 sensor varies the voltage within a range of about 1 volt, if the exhaust is rich, down through about 0.1 volt if the exhaust is lean". Lean error is thrown for voltages less than 0.2; rich error when voltage is greater than 0.7.
Are those values the ecm voltage + sensor reading? Or just the sensor reading?
My sensor shows about 0.6 volts after releasing the throttle [which should be a fairly rich state]. Most of the time [idle to 2000 RPM while in park] my sensor is reporting 0.01 to 0.1 V. I would be surprised if the engine is running lean all the time. Maybe? Do those values seem reasonable?
I just picked up a remanufactured ecm. I'll give it a shot once I understand what I am looking for.
Last edited by ChadK89; Jul 29, 2024 at 08:44 PM.
Race Director
Joined: Jun 2004
Posts: 13,960
Likes: 707
From: WI
Those values do seem reasonable tho if someone could check theirs and verify that would help. I did have a car with an odd reading from a washer stuck in the exhaust valve anything like that could be going on? Try plugging in the reman ecu see what happens.
Race Director
Joined: Jun 2004
Posts: 13,960
Likes: 707
From: WI
I found my old thread on the code 13 odd issue I had. Miss these old members!
https://www.corvetteforum.com/forums...-to-do-it.html
https://www.corvetteforum.com/forums...-to-do-it.html
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
8th Gear
Joined: Jan 2021
Posts: 8
Likes: 0
From: Illinois
Progress got delayed a bit because the first ecm that I obtained couldn't start the engine. That seemed like a worse problem than a "service engine soon" light, so I replaced with my original ecm.
Now 1 month later, I just got a different replacement ecm. This time, the engine started right up. I went for a short drive after warming the engine temp to around 180 F. Weather was unseasonably cool, so during my highway cruise, the temp was around 170F. But no SES light during the 15 minute drive. Very good news, but not 100% convincing.
Today, I disconnected the o2 sensor and turned the key to 'on' position without starting the engine. I hooked up my voltmeter to the wire coming from the ecm and grounded it to the frame. My meter didn't make a perfect connection with the wire, but I saw voltages around 0.3 V. That's reasonably close to what the manual says (around 0.45V).
So, I think this is fixed for now. Rejoicing! Thanks for the input here.
Do any ecm reman companies still work on 80s GM ecms? Would they know what is to be fixed for my original ecm?
Now 1 month later, I just got a different replacement ecm. This time, the engine started right up. I went for a short drive after warming the engine temp to around 180 F. Weather was unseasonably cool, so during my highway cruise, the temp was around 170F. But no SES light during the 15 minute drive. Very good news, but not 100% convincing.
Today, I disconnected the o2 sensor and turned the key to 'on' position without starting the engine. I hooked up my voltmeter to the wire coming from the ecm and grounded it to the frame. My meter didn't make a perfect connection with the wire, but I saw voltages around 0.3 V. That's reasonably close to what the manual says (around 0.45V).
So, I think this is fixed for now. Rejoicing! Thanks for the input here.
Do any ecm reman companies still work on 80s GM ecms? Would they know what is to be fixed for my original ecm?
