bp91z28

ok i have been troubleshooting my cooling fans not turning on and when i was doing continuity checks to the ecm harness i saw in the haynes the part were it said about the chip and ecm matching. so i open it up and this is what i see. the ecm sticker says SERV# 01227730 BATZ 88BATZ M310087046 and the chip says DELCO AWFU 5509 and to make things even wierder. if i short out the diagnostic pins my secondary fan turns on. WTF!! i have only owned this car since november and have found many things that confuse me about this car. so it doesnt surprise me that this is all messed up. also?? my speedo does not show correct speed. the previous owner said there was a 89 iroc rear end. well i found out a few days ago that is a 88 rear. sorry i went off on a tangent. so my question is could this mismatch be causing my fans to not turn on. also how much am i looking at spending to fix this. well i guess first thing first find out which part is correct. thanks bryce

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91 camaro z28 305 TPI & 700R4
header's, mac exhaust w/ high flow cat, crane cam fireball hi-6 ignition, b&m 2200 stall converter, b&m shift kit, msd wires, bosch 4's, front mount trans cooler, ram air mod, and 323
rear end from a 88 iroc.

15.525 @ 92.87

RBob

As for the ECM and the chip it is OK that they do not match. In your case the ECM was replaced while the chip (AWFU) is correct for your car (could we have fun with that BCC name).

The secondary fan turning on with the A/B shorted is good. That means the circuitry and relay are good for that fan. The other fan is controlled by the fan switch in the pass side cyl head.

And the A/C figures in here somehow too. IOW the A/C pressure switch will also enalble one (or both) of the fan(s).

Speedo off, see trans board, need to change a small gear in trans as the rear change also changed the rear end gear ratio.

ECM wiring can be found at www.diy-efi.org/gmecm

Welcome aboard,

RBob.

RBob

The fan wiring can be found here:

ftp://ftp.diy-efi.org/pub/gmecm/manu...730v8tpi-4.jpg

The ECM controlled fan will not come on until 226°F to 235°F, calibration dependent.

The wiring diagram will show how the head coolant switch along with the A/C pressure switch control the other fan.

Note that the temperature these fans come on is high, and the dash gauge is not a indication of the real coolant temperature.

RBob.