BoostJockey

Hi folks,
I bought a 97 civic with an LSV swap last week. Car came to me w/o an ECU and a few other problems. After getting most the car back 2gether I decided to try and get her started and borrowed the ECU from my other car. Its a 96 civic with 99 GSR swap, running full OBD2. Mostly stock, no problems/CELs, wired good w/ butterflys and all

So I hook my ECU to the new project and it starts but ran like crap. I shut her down and check the DTCs. Had 3 codes, primary O2 heater circuit, secondary O2 heater circuit, and P0335 "Crankshaft Position Sensor Circuit Malfunction."

The O2 codes are prob an easy fix. I started walking through the service manuals troubleshooting guide and get to the final step, Replace with Known Good ECU.

Well, when I put the ECU back in my daily it brought code P0335 with it. I ran thought the trouble shoot in this car with the same result = replace ECU.

What would cause this? Is there any way to repair this ECU? I need it to get through inspection and both these cars are due. I have a chipped OBD1 ECU coming but Im scared to put it in, and it wont pass inspection here. Please help me out guys. Thanks
Dave

HondaPartsHero

Have you reset the ECU to see if they come back?

BoostJockey

Yes. I have tried the ECU again in both cars. When I put the key on, no CELor DTCs. After I start the car, P0355 comes up right away. Its gotta be in the ECU? Any fixes for OBD2 ECUs? Found a simiar threads that pointed to a fix on the circuit board, but it was for OBD1.

BoostJockey

UPDATE: I tried another ECU, this one was a friends from a 95 civic LX m/t. Its OBD1 and we used a known werking conversion harness. Same code came up and permanently stored. I accomplished nothing 2day but fry TWO ECUs!

I have walked though the code's trouble shoot on 3 cars from the Honda service manual. It was done on 3 vehicles and appropriate manual used (96 and 92-95).

The car thats killing the ECUs is new to me, never even driven it. Its a 97, and I think its go the original harness but it has been converted at the dizzy to OBD1. The only thing I can think of is to swap the guts of this dizzy with a know good OBD1 dizzy and try it again and see if it will fry another ECU.

Please help me out, I know someone out there must know something, a car burning codes in ECUs. Ive got 3 cars running like crap and Im out of ECUs.

Wrona

did u actually reset the ECUS and not just plugged them back in u have to reset them by unhooking the battery cause the codes are stored inthe memory of the ECU

BoostJockey

Yup. done by battery and handheld tester in more than one car. Once you put an ECU (OBD1 or 2) into this car it will throw the CEL P0335 FOREVER, no matter what car u try it in. Once the motor starts, the code is back.

Former User

P0335 indicates a problem in the CKF sensor circuit. The OBD2 ECU looks for a CKF sensor but an OBD1 ECU does not. So I am puzzled when you say that an OBD1 ECU also threw OBD2-specific CEL code P0335.

BoostJockey

Using a OBD2 >1 adaptor harness and a P06 ECU, it threw code 4. Didnt bother w/ handheld tester. Just blinked it (4 short). So its equivalent to P0335 or P0336. That code now comes up from both ECUs (P06 and P72) in any car Ive tried it in.

BoostJockey

BTW page 11-54 of my service manual says P0355 is Crankshaft Position Sensor Circuit Malfunction. P1336 and P1337 are for Crankshaft Speed Fluctuation Sensor.

Former User

My mistake -- you are correct. I was led astray by this typo in the service manual:






Anyway, for the car eating ECUs, use a multimeter to test both CKP wires for a short. Do the short tests from each of the two ECU terminals for the CKP.

BoostJockey

Im just glad ur tryn to help. Theres no short to ground on the 6 sensor wires from the dizzy to ECU. I can give more details but thats the simple version. I checked both dizzy and ECU plugs to batter neg. Aslo did resistance from dizzy to ECU plug, nothing higher than 4ohms and I assume cause I had to use a paper clip and a cheap skinny test lead.

Former User

For this discussion, only the two CKP wires are relevant. It may help if you were to detail exactly how you tested for a short to ground on those wires. What was unplugged and what was still plugged in when you did the short tests? What wire terminals were tested? What were the Ohm readings?

BoostJockey

I just typed for an hour and HT wouldnt let me post w/out refreshing and a lost it all. So heres a condensed rewrite.

Rechecked path to ground w/ key off, All ECU and dizzy connectors unplugged. Meters black lead clpped to battery neg. The meter reads Open Lead when red lead is in contct with.

ECU CONNECTOR C (OBD2A)
# 2 CKPP, BLU
#12 CKPM, Wht

Vehicle Dizzy plug (OBD1)
# 2 Crank Output, Blu/Grn
# 5 Crank Ground, Blu/Yel

I got a new ECU in the mail 2day but Im too scared to plug it in. This car killed the last 3 ECUs that were tried. I just finish swapping new guts into the dissy housing and will compare some more readings. Pls any ideas chime in.

Former User

Doing the same tests for a short from the terminals of the unplugged ECU connector, do you get identical results with the distributor installed and the distributor connector plugged in?

BoostJockey

With the dizzy plugged and the ECU unplugged, there is no continuity to ground at ECM connector C, terminals 2,3,4,12,13,or 14. This is with new guts in the dizzy. I have the old one in a ziplock with the plug sticking out for testing. Car is running good(for limp mode) with a computer that has the code. Any way to besure I wont fry another ECU? Id rather pull the motor and swap the harness before I burn another.

So whats my next step? and is there anyone out there that fixes OBD2 ECUs?

Former User

Check whether any sensor connectors are swapped - IACV, TPS, MAP, ECT, IAT, EVAP, PS pressure, VTEC, etc.

BoostJockey

K, Ill get back to you with a list, but it might be a lil long. I can tell you rite now the map is hanging from vaccume line under a victor x mani, the IAT is swinging free on the harness with a second sensor plugging the manifold, thers no 2nd O2, ect.

Former User

A swapped or shorted sensor connector could be frying your ECU. I'd recommend that you put ALL of your sensor wiring in proper order before installing a replacement ECU.

BoostJockey

I started going thru the sensors, have some new ones comming, but so far nothing that looks like it would fry the crank position circuit (if thats what happened). So before I go thru the sensors, heres a lil more info on the dizzy/CKP wiring.

There is an aftermarket tach on the dash. It gets a lil jumpy when cranking but is smooth when motors running. Its tied in behind the cluster and is tapped into the harness with those plastice t taps. They were all making good contact so I left them and wrapped with a lil tape.

The car has a massive alarm and I assume remote start since somethings bypassing the clutch safety. Wouldnt that tap into the RPM wire? Im gonna have to get the wiring diagram for the alarm and pull parts of the system I dont want. Im gonna have to get more familar with the system first, theres 3 brain boxes and I dont even know what they all do (GPS?).

I resoldered and heat shrank the RPM and 2 CKP sensor wires where the harness had been converted to OBD1. Resistance b/t the ECU plug and dizzy plug are.

Dizzy Plug ECU
Blu/Grn -> Blu Pin C2, CKPP (Blu) = 3.8ohm
Blu/Yel -> Wht Pin C12, CKPM (Wht) = 2.8ohm

From where the dizzys sensor wires were converted the Grn, Blu, and Yel wires go into an orange shielded tube (in factory harnesses) and emerge unmolested a few inches before the ECU.
Anyone more ideas or tests?
Anybody fix my ECUS?

Former User

You should continue to verify that NO sensor connectors are swapped. You've clearly shown that the CKP sensor circuit does not have a short. Therefore, a short in another ECU/sensor circuit is frying an area of the ECU that evaluates the CKP sensor circuit for problems.

Start by soldering and shrink wrapping this wire splice.

It's always a good idea to sort out aftermarket alarm system wiring.

A wire short not an open would blow the ECU, so you should be testing wires accordingly (i.e., for continuity to body ground rather than for continuity).

BoostJockey

Can you explain more about what u mean by sensors being "swapped." Like TPS and MAP plugs, or different sensor models? I dont wanna start looking for the wrong thing.

Former User

Some sensor connectors are interchangeable, i.e., they can fit where they should not. This poor design has contributed to many a blown ECU.

boostedef123

These are the reasons why masking tape and a sharpie works wonders.

Eg5ir1

Yes old thread I know but I just ran into the same problem so I'm wondering if BOOSTJOCKEY solved the issue.