Flashing “Auto Trans” light and ECM (Engine Control Module)
Posted: Wed May 01, 2013 8:19 pm
On my 1993 Bighorn (3.2L petrol [added]), I have for some time had an intermittent flashing of my “Auto Trans” light, and it jumping into, or staying in, limp-mode 3rd gear.
It stays off or “a while” after I turn off the ignition and restart, but then it comes back unpredictably. For example, two months ago, it happened 10 times between Wanganui and Stratford, but not at all from Stratford to New Plymouth to Lower Hutt. Hutt Automatics could find no stored DTCs (Diagnostic Trouble Codes), nor any evidence of burnt transmission oil.
Then this last week it happened once between Lower Hutt and Rotorua, then daily within 20 metres of morning starts in Rotorua (so not a temperature problem), and then about 20 times between Rotorua and Bulls, but after my “fix” (described below) not at all between Bulls and Lower Hutt! My question is, was my fix really a fix?
In Bulls, I noticed that the engine would not idle, and would only run at driving speeds. So I started to think. I figured that there may be an ECM problem, so I stopped, disconnected and reconnected the battery to re-initialise the ECM and possibly the TCM. After this, it idles normally, and there is no more flashing of the “Auto Trans” light (at least not so far – touch wood!). But did I really fix anything?
And if this sort of thing happens again from time to time, should I install a battery master switch so that (eg if it’s raining) I would have fast way of re-initialising the ECM and possibly the TCM? And if I do this, should I install it on the positive or the negative battery terminal? And what current rating switch should I buy (100 amps or 200 amps)?
Many thanks for any comments or suggestions.
It stays off or “a while” after I turn off the ignition and restart, but then it comes back unpredictably. For example, two months ago, it happened 10 times between Wanganui and Stratford, but not at all from Stratford to New Plymouth to Lower Hutt. Hutt Automatics could find no stored DTCs (Diagnostic Trouble Codes), nor any evidence of burnt transmission oil.
Then this last week it happened once between Lower Hutt and Rotorua, then daily within 20 metres of morning starts in Rotorua (so not a temperature problem), and then about 20 times between Rotorua and Bulls, but after my “fix” (described below) not at all between Bulls and Lower Hutt! My question is, was my fix really a fix?
In Bulls, I noticed that the engine would not idle, and would only run at driving speeds. So I started to think. I figured that there may be an ECM problem, so I stopped, disconnected and reconnected the battery to re-initialise the ECM and possibly the TCM. After this, it idles normally, and there is no more flashing of the “Auto Trans” light (at least not so far – touch wood!). But did I really fix anything?
And if this sort of thing happens again from time to time, should I install a battery master switch so that (eg if it’s raining) I would have fast way of re-initialising the ECM and possibly the TCM? And if I do this, should I install it on the positive or the negative battery terminal? And what current rating switch should I buy (100 amps or 200 amps)?
Many thanks for any comments or suggestions.