Hello to all,

My ’91 Civic DX, 1.5L, Dual Point EFI, auto-trans, is throwing code 12 from the ECU. First, some history. I purchased this car about one month ago, and it had a blown head gasket, among other deferred maintenance. I removed the head and had it resurfaced, just to be sure it was flat. At this time gaskets, valve stem seals and necessary adjustments/repairs were performed. I replaced the thermostat, water pump, timing belt, misc. timing/drive belts, O2 sensor, ign. wires, plugs, dizzy cap and rotor, all rubber hoses and so on. I cleaned the IACV and replaced the PCV valve. I found the previously installed (old) PCV valve to be completely blocked. I ran the engine while still on jack stands for about two hours total, after which I changed the oil and filter. On its first drive following the above work, code 12 was thrown by the ECU, two blocks from home, even though it did not throw this code or any other while I tested it during the initial two hour run. I reset the ECU and it ran fine for another couple of blocks and threw the code again. I looked up this code in my Haynes manual and it tells me it pertains to the EGR system. I have searched for an EGR valve or whatever they use in place of it to no avail. All I have found is a cluster of relays and such near the firewall, on the passenger side, above the fuel filter.

Can someone please give some suggestions as to what to look for?

Cheers,
Norman C

 

You seem like you know what you're talking about. EGR system would be attached to the exhaust many, and attached to the throttle body. I have a DPFI and on mine there is a diaphragm behind the throttle assembly, which is operated by a plunger attached to the throttle. this plunger/diaphragm may not be for the EGR, but it is my best guess. good luck!