1994 ZR1 Code H64 - ZR-1 Net Registry Forums

Zedder94 · 08-02-2022

Hi guys,

Wanted to reach out to you all and ask a couple questions. My 94 ZR1 is throwing a H64 code (As you all know - RHS Front O2 sensor lean). It will come in after it has warmed up and goes into closed loop operation, approx 10 minutes of driving. The car has 63K miles. No rough idle or rough running through the rev range.

From my research i was going to replace the RHS O2 sensor (prior to the CAT) After getting under the car the O2 sensor is in a shocking position to access! Any info or secrets on getting to the sensor? I was thinking of dropping the CAT to do so. I cannot see any other way.

I was thinking the O2 sensor would be the easiest try at fixing the code, I have read on here that injectors could cause it also. Wanted to change out sensor prior to injectors.

Any info is appreciated fellas. Cheers,

Jay.

Zedder94 · 08-04-2022

Cmon guys, No one ever had and rectified the old H64 code?

zyal8r · 08-05-2022

Mine may have gone away on its own somehow.

When I got my '95 (5600 miles) in August, I had three codes, C12, H22, H64. My CEL was on constantly with a high idle. I've since corrected the high idle (TPS calibration as voltage was high), filled it with freon (I know this probably has NO relation but I needed A/C!) and have put about 80 miles on it in the last month. It is running MUCH better and the CEL has not come on for a while, come to think of it. My scanner (Snapon) lists TPS slightly low code at .52v and one other code (46) which says antitheft system problem - no idea what that is and haven't tested the alarm.

Honestly couldn't tell you how my H64 went away - I did a lot of vacuum troubleshooting to identify the high idle before I figured out the TPS issue. But I will keep watching for any new codes.

Sorry this probably isn't any help - more of a head scratcher than anything!

Mike

Zedder94 · 08-06-2022

Thanks Mike, Ill keep digging.

Zedder94 · 12-24-2022

Righto, for anyone who has the same headache ill post what fixed my 94...

Ended up changing the RHS O2 Sensor but still no fix...Ended up changing the fuel filter and performed a Fuel PSI test driving and at WOT with the specs from ZR1specialist website. (Great info on there)

No more code or engine lights. Car runs great.

secondchance · 12-24-2022

I have a 94 but got rid of factory exhaust manifolds and exhaust a long time ago. As such, difficult O2 sensor is a long forgotten memory.
If right side lean persist post sensor replacement, I would suspect injectors.
My 2 cents.

Zedder94 · 01-02-2023

Quote:

Originally Posted by secondchance

I have a 94 but got rid of factory exhaust manifolds and exhaust a long time ago. As such, difficult O2 sensor is a long forgotten memory.
If right side lean persist post sensor replacement, I would suspect injectors.
My 2 cents.

Thanks mate. Appreciated.

08-02-2022	#1
Zedder94 Join Date: Jun 2022 Location: Arroyo Grande CA Posts: 8	1994 ZR1 Code H64 Hi guys, Wanted to reach out to you all and ask a couple questions. My 94 ZR1 is throwing a H64 code (As you all know - RHS Front O2 sensor lean). It will come in after it has warmed up and goes into closed loop operation, approx 10 minutes of driving. The car has 63K miles. No rough idle or rough running through the rev range. From my research i was going to replace the RHS O2 sensor (prior to the CAT) After getting under the car the O2 sensor is in a shocking position to access! Any info or secrets on getting to the sensor? I was thinking of dropping the CAT to do so. I cannot see any other way. I was thinking the O2 sensor would be the easiest try at fixing the code, I have read on here that injectors could cause it also. Wanted to change out sensor prior to injectors. Any info is appreciated fellas. Cheers, Jay.

08-04-2022	#2
Zedder94 Join Date: Jun 2022 Location: Arroyo Grande CA Posts: 8	Re: 1994 ZR1 Code H64 Cmon guys, No one ever had and rectified the old H64 code?

08-05-2022	#3
zyal8r Join Date: Oct 2019 Location: Raymore, MO Posts: 117	Re: 1994 ZR1 Code H64 Mine may have gone away on its own somehow. When I got my '95 (5600 miles) in August, I had three codes, C12, H22, H64. My CEL was on constantly with a high idle. I've since corrected the high idle (TPS calibration as voltage was high), filled it with freon (I know this probably has NO relation but I needed A/C!) and have put about 80 miles on it in the last month. It is running MUCH better and the CEL has not come on for a while, come to think of it. My scanner (Snapon) lists TPS slightly low code at .52v and one other code (46) which says antitheft system problem - no idea what that is and haven't tested the alarm. Honestly couldn't tell you how my H64 went away - I did a lot of vacuum troubleshooting to identify the high idle before I figured out the TPS issue. But I will keep watching for any new codes. Sorry this probably isn't any help - more of a head scratcher than anything! Mike __________________ 1995 ZR-1 #004 - Yellow/Black 1996 LT4 #3828 - Yellow/Beige/LT4/Z51 - 1 of 4

08-06-2022	#4
Zedder94 Join Date: Jun 2022 Location: Arroyo Grande CA Posts: 8	Re: 1994 ZR1 Code H64 Thanks Mike, Ill keep digging.

12-24-2022	#5
Zedder94 Join Date: Jun 2022 Location: Arroyo Grande CA Posts: 8	Re: 1994 ZR1 Code H64 Righto, for anyone who has the same headache ill post what fixed my 94... Ended up changing the RHS O2 Sensor but still no fix...Ended up changing the fuel filter and performed a Fuel PSI test driving and at WOT with the specs from ZR1specialist website. (Great info on there) No more code or engine lights. Car runs great.

12-24-2022	#6
secondchance Join Date: Aug 2006 Location: McLean, VA Posts: 3,707	Re: 1994 ZR1 Code H64 I have a 94 but got rid of factory exhaust manifolds and exhaust a long time ago. As such, difficult O2 sensor is a long forgotten memory. If right side lean persist post sensor replacement, I would suspect injectors. My 2 cents.