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Super Moderator
1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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They may share the communications bus that shares information between modules. A fault code from the TCM (transaxle control module) may give us some clues. It sounds like the common thread here. The gauges would drop out when the bus goes down.
If you can get the TCM scanned for fault codes and a wiring diagram, you may be able to fix this.
The 'twisted pair' communications bus wiring would have its weakest spots at the terminals and connectors. Usually a violet and white wire pair. Look for corrosion, rub-throughs, pinches and wire breaks. Wet connectors can short a bus.
Being intermittent makes it harder to find.
 

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Super Moderator
1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
Joined
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24,231 Posts
The ECM (or PCM) is a different module read at a different connector than the TCM. The transaxle limp-in (2nd gear) cause may not show up on the engine controller (underhood connector). You want to scan the transaxle controller - TCM (underdash connector).
Being OBD 1, you will need a capable scan tool with the Chrysler-specific cables.
An engine fault may light the 'ck eng' light and show codes via the key-dance, but a transaxle fault may not.
 

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Super Moderator
1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
Joined
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24,231 Posts
PCM is by the battery. TCM is on the right side firewall and the BCM is under the dash. They are modules. Actually disconnect and reconnect the connectors to 'scrub' the terminal contacts together.
 
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