ecm question

i was just woundering if an 88 cherokee base and cheif computers are compadable there are both auto's 4.0 ltr 4x4

should be. only difference on the two is the trim package i believe.

Should be. The difference between "base" and "Chief" is trim level - all else being equal, the engine controls will be the same. I'd be only mildly surprised, if the drivetrain options are the same, you'd find the same part number on the ECUs.

You'd probably find the same numbers on the manual and automatic ECU's - until 1991, the transmission control unit was divorced from the ECU anyhow...

5-90

The automatic and stick are different. The automatic ECU has some additonal outputs and inputs to the TCU. There is a speed signal out and a gear select in.

I'll have to review my FSM for details on the differences, then. But, I do know that the TCU was divorced until 1991 - when ChryCo integrated it into the SBEC (Single Board Engine Controller.)

But, with three A/T RENIX XJ's and one M/T, I really should sort this out...

5-90

langer1 said:

The automatic and stick are different. The automatic ECU has some additonal outputs and inputs to the TCU. There is a speed signal out and a gear select in.

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There are no inputs to the Renix controller that would affect operation of the auto trans. It does share data lines only to communicate with the scan tool. The manual trans ECU has an output for a manual trans shift light though I'm sure that's not needed/used with an automatic equipped XJ. The AW4 has it's own speed sensor (mid 98 added a input speed sensor for trans also) and reads the gear selector switch itself. The AW4 till it's last days (01) was a stand alone system (with with a minor exception of the 91-up sharing a TPS reading (spliced in parallel and uses the PCM's supply voltage for it). The 97-up had a data line to the PCM for turning the check engine lamp on if the trans controller had a code but it is not required for operation.


Mike R

One other differance is the TPS, at idle the Manual voltage is 1.25vdc while the Automatic ECU calls for 4.5vdc at idle.

langer1 said:

One other differance is the TPS, at idle the Manual voltage is 1.25vdc while the Automatic ECU calls for 4.5vdc at idle.

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Renix, yes the TPS is different. The automatic TPS is double sided and you adjust it on the trans side and the manual one you adjust on the engine side if you are doing it with a voltmeter (since there is no trans side) unless you have a scan tool in which case you adjust both on the engine side at 11-13%.


Mike R

MJR said:

Renix, yes the TPS is different. The automatic TPS is double sided and you adjust it on the trans side and the manual one you adjust on the engine side if you are doing it with a voltmeter (since there is no trans side) unless you have a scan tool in which case you adjust both on the engine side at 11-13%.


Mike R

Click to expand...

I am only referring to the engine side