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craftymatt · 01-13-2008, 11:56 PM

Swapped a B16a into a 91 CRX HF; OBD0 PR3 ECU

Anyway, I'm getting code 6 from the ECU (Defective Coolant temp circuit/sensor), and I can't figure out why. The sensor is plugged in, I've tried swapping the sensor (and tested the resistance of both sensors, they were the same), and I traced the connector pins back to ECU/ground. The car runs okay but is obviously in limp mode (bad idle, 7200rpm rev limit, no VTEC etc).
If I use the old HF ECU (PM8) it does NOT throw the code and runs much better (indicating that it is reading the ECT correctly).
I've searched around to see if maybe on some of the PR3's the coolant temp sensor came in on a different pin, but that doesn't seem to be the case. Why else would this happen? Bad ECU? ECU code is 37820-PR3-003, is 003 some weird revision or something? I opened the ECU up and nothing appears to be damaged/modified.

LS_VTEC · 01-14-2008, 03:37 AM

Is the sensor bad? Did you test for resistance in the circuit itself? Is there sufficient coolant in the engine?

CRX18703 · 01-14-2008, 01:42 PM

Its probably a lose ground, i had the same problem with minds

**riceburner89** · 01-14-2008, 09:09 PM

Thermostat?

LS_VTEC · 01-14-2008, 11:40 PM

Quote:

Originally Posted by riceburner89

Thermostat?

The thermostat wouldn't cause a code-6, it just opens when the coolant reaches a specific temperature.

craftymatt · 01-17-2008, 05:04 PM

figured it out!!!

Turns out on the HF there is a wire coming into the ECU (B9 on the ECU connector) that tells the ECU when the car is in reverse. Every time I went into reverse (which happened to be every time since I had to back out of the driveway when I wanted to drive it) it would apparently freak out the ECU and it would trigger a code 6. This also explains why the HF ECU didn't have a problem.

Anyway, I pulled B9 from the connector and now the car runs great. Finally I can hit VTEC!!!

01-13-2008, 11:56 PM	#1
craftymatt Junior Member Join Date: Jan 2008 Posts: 6 iTrader: 0 / 0% Rep Power: 0	B16 CRX throwing code 6 Swapped a B16a into a 91 CRX HF; OBD0 PR3 ECU Anyway, I'm getting code 6 from the ECU (Defective Coolant temp circuit/sensor), and I can't figure out why. The sensor is plugged in, I've tried swapping the sensor (and tested the resistance of both sensors, they were the same), and I traced the connector pins back to ECU/ground. The car runs okay but is obviously in limp mode (bad idle, 7200rpm rev limit, no VTEC etc). If I use the old HF ECU (PM8) it does NOT throw the code and runs much better (indicating that it is reading the ECT correctly). I've searched around to see if maybe on some of the PR3's the coolant temp sensor came in on a different pin, but that doesn't seem to be the case. Why else would this happen? Bad ECU? ECU code is 37820-PR3-003, is 003 some weird revision or something? I opened the ECU up and nothing appears to be damaged/modified.

01-14-2008, 03:37 AM	#2
LS_VTEC you get the BRAKE Join Date: Dec 2007 Location: NJ Posts: 2,596 iTrader: 0 / 0% Ride: 99 YZF-R6 Rep Power: 40	Is the sensor bad? Did you test for resistance in the circuit itself? Is there sufficient coolant in the engine? __________________ eg hatch (jdm b16) sold 1999 Yamaha YZF R6 (modded) http://hondaswap.com/engine-building...ow-pics-102486 sold

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01-14-2008, 01:42 PM	#3
CRX18703 CT'sFinest Join Date: Jan 2008 Location: New Haven CT Posts: 7 iTrader: 0 / 0% Ride: 1991 Honda CRX SI Rep Power: 0	Its probably a lose ground, i had the same problem with minds

01-14-2008, 09:09 PM	#4
riceburner89 Banned Join Date: Jun 2007 Location: santa clarita CA Posts: 91 iTrader: 0 / 0% Ride: 1995 honda civic DX coupe Rep Power: 0	Thermostat?

01-17-2008, 05:04 PM	#6
craftymatt Junior Member Join Date: Jan 2008 Posts: 6 iTrader: 0 / 0% Rep Power: 0	figured it out!!! Turns out on the HF there is a wire coming into the ECU (B9 on the ECU connector) that tells the ECU when the car is in reverse. Every time I went into reverse (which happened to be every time since I had to back out of the driveway when I wanted to drive it) it would apparently freak out the ECU and it would trigger a code 6. This also explains why the HF ECU didn't have a problem. Anyway, I pulled B9 from the connector and now the car runs great. Finally I can hit VTEC!!!

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B16 CRX throwing code 6