Hallo to everybody !
I swapped my 870-ECM for a 165-ECM, did the right wiring and now I get always code 36 ( MAF-burnoff-circuit ). After shutting the engine off, a few seconds later the MAF-Burnoff-Relay engages, there is 12V at MAF-Sensor PIN-D and Pin-E, but only for 1 second ( or even shorter ). How long should the burnoff-circle last ? What else could be the problem for the code 36 ???
Thanks, Uwe

 

The signal from the ECM to the burnoff control relay should only last long enough for the MAF to generate a high signal level on the 'C' terminal. That is teh method the ECM uses to verify that the MAF has completed an effective burnoff cycle.

I have seen on rare circumstances the burnoff cycle fail due to an intermittent auxilliary oil pressure switch or failing neutral safety switch. The ECM needs to detect NO voltage on the fuel pump sense input during the burnoff cycle, or the cycle will be terminated. The neutral safety switch must also detect a PARK/NEUTRAL position for the ECM to complete the burnoff cycle.

 

I did some more tests : PIN B12 at ECM ( MAF Sensor Input ) with Key on, Engine Off : 4,6 Volts ( ist this okay ? ). I manually grounded PIN D12 ( Burn-Off Relay Control ) : 12 Volts at Pin D and E at the MAF-Sensor, I can see the wire glowing, but at the ECM at PIN B12 there is 0 Volt ( shouldn´t there be 5 Volt to make the ECM "see" the successful burnoff-cycle ? ). Do I have a bad MAF-Sensor or a bad ECM ? What else can I check ?
Thanks, Uwe

 

Your tests of terminal E and D on the MAF are valid, and those are the correct voltages for a burn off cycle.

The 1985 Delco MAF generates a 5VDC square-wave output that is modulated in output frequency based upon the measured air flow. If measured with a voltmeter, the voltage will vary due to the RMS averaging of the meter and duty-cycling of the output. This would give the appearance of an analog output. Many DMMs will try to RMS average the voltage on an AC scale or read the pulsating voltqage on the DC scale as something slightly lower than the actual P-P voltage, depending on the sampling rate of the meter. If you use a true RMS DMM (like a Fluke 8026B), the voltage will remain steady at around 3.0-4.0 VDC. At a high intake (MAF) flow, the frequency is much higher, and most handheld meters will not be able to read the voltage. Even if the meter could read the P-P voltage, the indication would be meaningless, since the frequency of the output is what matters.

The ECM input ignores the apparent voltage variation and counts the number of pulses directly, rather than converting them to "counts" internally. If the MAF output is checked with an oscilloscope, the waveform is a variable frequency square wave at about 50% duty cycle that peaks around 5VDC. If you have a frequency counter on your meter (or as a separate unit) or have an oscilloscope, you can test the MAF output frequency. At idle, the output is typically around 35-40 Hz, and at peak flow, the output should be closer to 100Hz.

Unfortunately, with the information you have thus far, no decision can be made.

 

Vader, thank you for your reply, but I have a 1985 TPI-Camaro with a original Bosch-MAF. ( Sensor-Output between 0 and 5 Volts ). By the way, I thought the Delco-MAF has no burnoff function ???
Thanks, Uwe

 

Uwe,

MOST 1985 TPIs used the Delco FM MAF sensor, except for a very rare few and very late production TPIs. What are the part numbers on the MAF sensor itself (ALL the numbers)? Does it look like this?

 

Vader,
I checked my MAF today :
Bosch
0 280 213 002
14 081 243
I have the original Bosch-MAF-Sensor. Will the Wells-MAF ( P/N SU-145 ) fit ? Can I order it online ?
Thanks, Uwe

 

14081234 is the GM OEM part number for a 1985- only MAF, which is the digital (frequency modulation) unit. The Wells SU-145 is not designed as a direct replacement for that type MAF. The data listed at the Micro-Tech web site is mistaken.

Incidentally, a new replacement Bosch MAF is $1,344.79 at Rock Auto, whereas the AC/Delco unit is only $479.79 : http://www.rockauto.com/catalog/cata...&parttype=5128

Either way, I'd do a lot of analysis before just bolting on a new MAF as a guess.

 

The 1986-89 MAF is a completely different unit:

http://www.rockauto.com/catalog/cata...&parttype=5128

This is the MAF sensor that should be used with the 1227165 ECM. Provided you repinned the harness or replaced the wire harness with the later type, the analog sensor should work. The 1985 digital MAF will not, however, and that may be your problem.

 

My MAF works allright with the 165-ECM, I get no code 33 or 34, my scanner shows the correct Air Flow Rate. The only problem I have is the code-36 burnoff-error, but the burnoff-circuit is working ... but the ECM doesn´t realize it. Can I disable the code-36 in my chip ??? ( I have a custom-burned chip, $32B-ECU).
Thanks, Uwe

 

If my understanding is right, I have a digital MAF on my car and from 1986 on they changed to analog MAF´s ??? Can anybody confirm this ?
What´s about the flag in the $32B-Mask called :"Analog MAF Meter in use" ( this flag is checked, should I remove this to make my ECM work with my digital MAF ? )
Uwe